Illinois 2006 Five Percent Report

This report is in response to the Federal requirement that each state describe at least 5 percent of its locations currently exhibiting the most severe highway safety needs, in accordance with Sections 148(c)(1)(D) and 148(g)(3)(A), of Title 23, United States Code. Each state’s report is to include potential remedies to the hazardous locations identified; estimated costs of the remedies; and impediments to implementation of the remedies other than costs. The reports included on this Web site represent a variety of methods utilized and various degrees of road coverage. Therefore, this report cannot be compared with the other reports included on this Web site.

Protection from Discovery and Admission into Evidence—Under 23 U.S.C. 148(g)(4) information collected or compiled for any purpose directly relating to this report shall not be subject to discovery or admitted into evidence in a Federal or State court proceeding or considered for other purposes in any action for damages arising from any occurrence at a location identified or addressed in the reports.

Additional information, including the specific legislative requirements, can be found in the guidance provided by the Federal Highway Administration,
http://safety.fhwa.dot.gov/safetealu/fiveguidance.htm.

Highway Safety Improvement Program

5 Percent Report

Prepared for
State Safety Engineer
Illinois Department of Transportation
Prepared by
CH2M Hill
Chicago, Illinois

September 2006

Introduction

Section 1401 of SAFETEA-LU amended Section 148 of Title 23 USC to create a new Highway Safety Improvement Program (HSIP) as a core FHWA program with separate funding. The purpose of HSIP is to reduce fatalities and serious injuries on public roads. As part of the new HSIP, States are required to submit an annual report to the FHWA describing not less than 5 percent of their highway locations exhibiting the most pressing safety needs. FHWA is providing guidance for the process and contents of the report. According to FHWA, the 5% Report should address the following in each state:

· Locations where severe crashes, including specifically fatalities, are clearly overrepresented (referred to as 'hazardous locations')

· Potential remedies to the hazardous locations identified;

· Estimated costs of the remedies to address the severe crashes; and

· Impediments to implementation of the remedies other than cost.

The intent of the 5% report is to gain an understanding of the nature and extent of safety problems, provide guidance to the states for where safety investments are needed, and provide a basis for tracking the progress toward improving safety in each state.

FHWA has required states to submit their draft report no later than August 31, 2006 to enable FHWA to review, compile and prepare their report to the U.S. Congress, which is due no later than October 1, 2006.

CH2M HILL is under contract to the Illinois Department of Transportation (IDOT) to provide services as required in support of the State's safety program. As part of this assignment, IDOT has asked CH2M HILL to assist in developing the State's "5% Report." This document presents the results of the CH2M HILL's efforts in this regard.

Study Parameters

The limited time to conduct the study to meet FHWA deadlines influenced the approach to the work. Data necessary to complete a study of this nature include locations of crashes, details of crash characteristics, roadway geometry information, and traffic volume data for the locations of interest. Only readily available data from IDOT's computer systems were used; no field data collection or verification was possible within the time frame to prepare the report. Also, IDOT's data records as of 2006 include geo-referenced data for the state system only (i.e., it was not possible to identify locations of crashes on the local roadway networks). Finally, as of spring of 2006 when this study was initiated only crash data from 2003 and prior years were available.

Given the above limitations the following decisions were made with respect to the conduct of this study. Future annual updates of this study should fill in and update the resulting gaps in study coverage:

· Crashes occurring on local roadways have not yet been geo-coded in the State database. Therefore, it was only possible to address roads other than U.S. and State highways in a general manner, by county.

· In terms of vehicle miles of travel (VMT) or exposure, freeways are the safest of all types of roadway. The analysis of freeway segments, therefore, was constrained to investigation of acknowledged problems involving specific types of crashes.

· IDOT has already retained CH2M HILL to identify high-risk locations and determine countermeasure for the most hazardous intersections in the State. This project is underway, but would not be completed in time for inclusion in this year's 5% Report. It was decided to continue with the intersection study as it has already been established, thereby deferring intersection findings until later in this calendar year.

Study Approach

FHWA has encouraged states to focus on problems that relate to severe crashes - those resulting in fatalities and serious injuries. Reference to and acknowledgement of a state's comprehensive safety plan is important. This translates to incorporating the full range of potential solutions to problems, including engineering and design measures, traffic law enforcement activities, and public education.

This study therefore looked at recorded crashes in multiple dimensions. Determination of locations with overrepresentation of crashes was one important aspect of the study. The second was a geographically based (on a county by county basis) evaluation of overrepresented high risk behaviors. Cost-effectively dealing with severe roadway crashes may involve both infrastructure improvements and specific locations or corridors; or sponsorship of enforcement and public education programs to address safety belt, impaired driving or other high-risk behaviors in certain general areas.

Overview of Basic Data

Data for the study included crash records, roadway inventory data, and traffic count information, all from IDOT records systems.

Crash Records

Crash records were furnished for the most recent five-year period for which data were available (1999-2003). The records contain information on the date and time of the crash, severity, environmental conditions, roadway and vehicle type, and crash type. Crash location was geo-coded for crashes that occurred on U.S. and State highways, but for crashes on local roadways, only local route name or number was obtainable.

The database included crashes that involved a fatality or an A, B or C-type injury^[1] and property damage only (PDO) incidents. Per direction from FHWA to focus on the more serious crashes, the analysis used a subset of the total database in which PDO crashes were excluded. All injury crashes were retained to enable sufficient numbers of crashes for deriving meaningful findings.

During the five-year period from 1999-2003, there were 419,029 fatal or injury crashes on Illinois roadways. Of these, 268,995, or 64 percent were non-intersection crashes and the remainder, 150,034 or 36 percent occurred at intersections. See Figure 1.

Figure 1. Illinois 1999-2003 Fatal and Injury Crashes by Facility Type

Roadway Inventory

Roadway feature data (2006) were furnished for all U.S., State, and local roadways in Illinois. The data were compiled from the Illinois Roadway Inventory System (IRIS) data system. The roadway data provided a variety of information on the characteristics of the roadway, the most important of which for this study were functional classification, length and cross-sectional features (number of lanes, presence of median).

Mileage of Illinois roadways by type is illustrated in Figure 2. Because crash records for the 1999-2003 analysis period were not geo-coded for local roadways, this initial 5% analysis pertains only to crashes occurring on U.S. and State highways (9 percent of total statewide mileage). Subsequent reports will be expanded to include the local roadway systems as discussed later.

Figure 2: Mileage of Illinois Roadways by Type

Traffic Counts

The Roadway Feature Inventory also contained, for each roadway segment, Annual Average Daily Traffic (AADT) as well as the year in which traffic was counted. The dates of traffic counts were predominantly between 2000 and 2005, but there were some earlier counts, mostly on low volume roads. The traffic counts in conjunction with the roadway cross-sectional feature were used to categorize segments for analysis.

Data Gaps

For this first annual 5% Report, the State is compelled to work with data that are already readily available. In order to comply fully with federal guidance in subsequent years, there are gaps in the existing database which will need to be filled. The manner in which this might be done is addressed later in this report. The most apparent of the existing data gaps are as follows:

· As stated previously, crash data for the local roadway system prior to 2004 is not geo-coded. IDOT's new Crash Information System (CIS) allows for coding of County mileage, and that data for calendar years 2004 and 2005 will be available before the end of 2006. Coding of past crashes on the local roadways needs to be expanded to allow locating each incident on the GPS roadway network. At this point, as shown below in Table 1, IDOT is not able to directly locate and evaluate 53% of fatal crashes on 89% of Illinois mileage.

· Crash records need to be more definitive in distinguishing between crashes that occurred at or in the influence area of an intersection, and those that occurred elsewhere.

· Improved currency in the availability of crash records is also needed. This study was not able to include data describing safety performance in 2004 or 2005. Improvements in the currency of crash records are being pursued by IDOT and are anticipated in future years.

· Enhancements to the Roadway Features inventory for may need to be considered to enable more robust analyses of potential countermeasures. Missing information includes data describing the roadside, intersection traffic control, and horizontal and vertical alignment.

Table 1: Mileage and Crashes by Severity by Roadway Type (1999 to 2003)

Roadway Type		Mileage	Crashes
Roadway Type		Mileage	Fatal	A-injury	B-injury	C-injury	Total
Freeway		2213	860	6473	15950	15514	38797
U.S./State	Rural 2-lane	7632	724	3973	7284	3473	15454
	Rural multi-lane	572	104	884	1915	1686	4589
	Urban 2-lane	1050	150	1617	4153	4164	10084
	Urban multi-lane	1335	389	4619	12078	13930	31016
	Sub Total	10589	1367	11093	25430	23253	61143
Local		100091	2504	28617	79936	57998	169055
Total		112893	4731	46183	121316	96765	268995

As indicated earlier, hazardous intersection locations and countermeasures are being considered under a separate IDOT project and are excluded, therefore, from this 5% analysis.

The number of non-intersection fatal or injury crashes that occurred in the five-year analysis period (1999-2003) on Illinois roadways is summarized by roadway type in Table 1 and shown graphically in Figure 3.

Figure 3: Crash Severity by Roadway Type for all Segments (1999 to 2003)

Analysis Methodology

The fundamental task was to identify homogeneous roadway segments with historic safety behavior indicating they are significantly worse than what should be expected. The following fundamental principles of roadway safety directed the analysis approach:

· Severe crashes are relatively rare events. As such care should be taken in identifying roadway segments that appear to be overrepresented in terms of severe crash experience. This translates to making sure that long enough time frames are used, long enough roadway segments are determined, and a high enough threshold of critical performance is defined.

· Expected or typical crash experience is a function of roadway type. Two-lane rural roadways have fundamentally different risk profiles than multilane urban arterials.

· Expected crash experience or safety performance is a function of traffic volume; but the relationship is complex, not linear, and varies with roadway type.

· Understanding types of crashes is important, not merely numbers or locations of crashes. Causes of and treatments for, say, single vehicle run-off-road crashes are different from rear-end or angle crashes.

· The severity of all crashes and particular crash types is important to understand.

It is well understood that crash rate (crashes per million vehicle miles) varies with traffic volume. Also, crash type characteristics vary significantly with different levels of traffic volume.

The scientifically accepted method for evaluation of crash and traffic information is to use frequency of crashes per unit length and time. 'Crashes per mile per 5 years' was adopted as the metric for characterizing high risk locations. To control for the effects of traffic volume on risk, roadways were segmented into ADT ranges. To control for and address differences in performance of different roadway types, the data were segmented by location (rural vs. urban) and roadway type (2-lane vs. multi-lane).

Roadway Segmentation Process

In order to analyze the roadway network, reasonable segments of roadway had to be defined. These segments served as the basic unit of analysis. Segments were defined for the entire length of U.S. and State highways in Illinois, with the exception of low volume two-lane rural State roadways. The U.S. and State roadway network was divided into four roadway classifications -two-lane and multi-lane rural roadways and two-lane and multi-lane urban roadways-and then again by ADT class. Each combination of roadway classification and ADT class was segmented separately. These segments had to be assigned manually due to inaccuracies in the GIS data.

The following rules were followed for assessing and assigning Segment IDs

1) Segments were at least 0.5 mile (2640 ft) long.

2) Segments that were less than 0.5 miles long, but were within 0.5 mile of another segment were assigned the larger segment's Segment ID. Any road that fell between these two segments was also assigned the Segment ID.

3) The same Segment ID for a road centerline was not to exceed a length of 4 miles (21120 ft).

4) Segments that had sharp turns were treated as two different segments. If the road appeared to be sharply curved, it was treated as one segment.

5) When possible, a new Segment ID was assigned at intersections. Possible exceptions included:

a. Segments not having an endpoint at an intersection

b. Segments less than 0.5 mile long at the intersection.

The following is a summary of the individual classes of roadways within which segmentation and analysis was performed:

2-lane rural roadways

1,500 vpd or less

1,501 - 2,500 vpd

2,501 - 4,000 vpd

4,001 - 6,000 vpd

6,001 - 8,000 vpd

8,001 - 10,000 vpd

10,001 vpd and greater

Multi-lane rural roadways

10,000 vpd and less

10,001 - 20,000 vpd

20,001 - 30,000 vpd

30,001 vpd and greater

2-lane urban roadways

10,000 vpd and less

10,001 - 20,000 vpd

20,001 - 30,000 vpd

30,001 vpd and greater

Multi-lane urban roadways

10,000 vpd and less

10,001 - 20,000 vpd

20,001 - 30,000 vpd

30,001 - 40,000 vpd

40,000 vpd and greater

For each ADT and roadway type class, a mean 'non-PDO crashes per mile per 5 years' value was computed. This number served as the benchmark for selection of high-risk segments within that ADT and roadway type class. Table 2 shows these average values for all mileage in the IDOT database.

Table 2: Mean Crash Rate by Roadway Type and ADT Class - Non Intersection/Non-PDO Crashes (1999 to 2003)

Roadway Type And ADT Class U.S. and State Roadways	Mean Crashes/Mile
Rural 2-Lane
Less than 1,500	0.2
1,501 - 2,500	0.4
2,501 - 4,000	0.6
4,001 - 6,000	0.8
6,001 - 8,000	1.1
8,001 - 10,000	1.8
10,001 and greater	2.2
Rural Multi-Lane
Less than 10,000	0.8
10,001 - 20,000	1.4
20,001 - 30,000	3.4
30,001 and greater	4.1
Urban 2-Lane
Less than 10,000	1.2
10,001 - 20,000	2.4
20,001 - 30,000	3.6
30,001 and greater	4.0
Urban Multi-Lane
Less than 10,000	1.1
10,001 - 20,000	2.5
20,001 - 30,000	4.1
30,001 - 40,000	5.4
40,001 and greater	6.3

Within each roadway type and ADT class, the segments with the greatest frequency of fatal and injury crashes were selected. All multi-lane rural roads and both two-lane and multi-lane urban roads were segmented. Due to the greater mileage of low volume two-lane rural roads, it was not possible to manually assign Segment IDs. Instead, a filter was applied to the lowest volume roads before segmentation. Separate plots were created of non-intersection, non-PDO only crashes that occurred on each of the lowest ADT classes of two-lane rural roadways. These plots were visually compared to a scale that showed twice the average rate for that ADT class. Segments with crash frequency at least twice the mean value were initially selected, representative of an estimated 5% chance of occurring. Locations that appeared to meet or exceed the critical crash frequency were highlighted and subsequently segmented for full analysis.

The mileage identified by this method represented slightly more than 5% of the ADT class mileage. This greater mileage was considered appropriate in that we expect some segments will be dropped from the analysis going forward for any number of reasons (e.g., with the study based on 2003 data some locations may have been treated or are programmed for treatment).

When crash rates for each individual segment were calculated, it was shown that the lowest rates for fatal and injury crashes (k+A+B+C) were less than twice the average for the ADT class, validating the method and showing that the locations with the highest crash frequency had indeed been captured. Subsequent checks for the higher ADT classes, for which all mileage was segmented, showed a very high correlation between frequency and severity of crashes, implying that most of the segments with the highest crash frequency had also been identified.

Table 3 summarizes the statistics for the selected segments and all mileage studied.

Table 3: Non Intersection/Non-PDO Crashes Per Mile (1999 to 2003)

Roadway Classification	All Segments Crashes/Mile/5 years	Selected Segments* Crashes/Mile/5 years
Rural 2-Lane*
Less than 1,500	0.8	2.2
1,501 - 2,500	1.3	3.7
2,501 - 4,000	1.7	4.8
4,001 - 6,000	2.6	7.1
6,001 - 8,000	3.7	8.7
8,001 - 10,000	5.7	11.5
10,001 and greater	11.0	29.6
Rural Multi-Lane
Less than 10,000	2.7	8.3
10,001 - 20,000	6.0	16.6
20,001 - 30,000	15.0	40.6
30,001 and greater	25.6	57.9
Urban 2-Lane
Less than 10,000	5.5	15.2
10,001 - 20,000	15.4	38.6
20,001 - 30,000	24.4	70.9
30,001 and greater	28.3	46.0
Urban Multi-Lane
Less than 10,000	5.3	18.5
10,001 - 20,000	13.0	37.8
20,001 - 30,000	26.5	70.5
30,001 - 40,000	34.5	71.6
40,001 and greater	42.4	110.9

*Final Selected Segments

Once segmentation was completed, 1999-2003 non-intersection, non-PDO crash frequency per mile was calculated for each individual segment. The Appendix contains plots of the crash frequency distribution for all ADT classes and roadway types. The plots confirm that the process indeed uncovered the most critical segments of roadway on the system defined in terms of concentrations of fatal plus injury crashes for the 5-year period studied. The segments were then ranked from highest to lowest crash frequency. The next step was to ensure that locations with the most severe crashes were appearing at the top of the list.

Refined Segments Based on Most Severe Crashes

FHWA direction for the analysis is to focus attention of states on the most severe crashes - specifically, fatal plus 'A-type' injury crashes. The list of approximately 6% of total mileage was further studied to provide this focus.

IDOT's method of weighting crash severity was used to determine a "severity index" for each analysis site. The IDOT formula for crash severity is:

EPDO = (50 x FC) + (50 X AC) + (5 x BC) + (2 x CC) + (1 x PDO)

Total Crashes

Where:

FC = Number of crashes where the most severe injury was a fatality

AC = Number of crashes where the most severe injury was an A (serious) injury

BC= Number of crashes where the most severe injury was a B (minor) injury

CC= Number of crashes where the most severe injury was a C (probable) injury

PDO = Number of crashes that were property damage only

Therefore, the weighting factors used in the IDOT calculation are:

Weighting Factor

Crash Type Weight

Fatal 50

A 50

B 5

C 2

PDO 1* (not included)

These weighting factors were applied to the crashes at each previously selected analysis segment to establish a rank order of sites by crash severity.

At this point in the analysis, two lists of sites had been developed for each roadway type by ADT class: 1) sites with the highest incidence of fatal or injury crashes, and 2) sites with the highest severity rating. Many of the same sites appeared on each list.

The method used to arrive at the final sample for each roadway class by ADT was to include sites appearing in descending order both by incidence and severity of crashes, until the composite length of the sites selected was equal to approximately six percent of total roadway length.

Table 4 shows the characteristics of the total mileage and final selected sample of high-risk locations for the Illinois system. Note that the high risk segments experience between two and four times the frequency of crashes of the overall system.

Table 4: Non Intersection Fatal plus A-injury Crashes Per Mile (1999 to 2003)

Roadway Classification	All Segments Crashes/Mile/5 years	Selected Segments* Crashes/Mile/5 years
Rural 2-Lane
Less than 1,500	0.2	0.8
1,501 - 2,500	0.4	1.4
2,501 - 4,000	0.6	1.8
4,001 - 6,000	0.8	2.4
6,001 - 8,000	1.1	3.3
8,001 - 10,000	1.8	3.7
10,001 and greater	2.2	5.7
Rural Multi-Lane
Less than 10,000	0.8	3.3
10,001 - 20,000	1.4	4.2
20,001 - 30,000	3.4	8.7
30,001 and greater	4.1	11.9
Urban 2-Lane
Less than 10,000	1.2	4.0
10,001 - 20,000	2.4	6.8
20,001 - 30,000	3.6	8.4
30,001 and greater	4.0	6.0
Urban Multi-Lane
Less than 10,000	1.1	4.4
10,001 - 20,000	2.5	7.8
20,001 - 30,000	4.1	12.8
30,001 - 40,000	5.4	14.3
40,001 and greater	6.3	17.5

*Final Selected Segments

Characteristics of the '5% High Risk' Sample

Using the processes described above, 406 analysis segments were selected on U.S. and State roadways. Characteristics of the analysis segments and total data base are summarized in Table 5. Total length of the analysis segments is 627.6 miles (about 5.9% of applicable mileage) for an average length per segment of approximately 1.5 miles. Length of individual segments varied from 0.8 to 3.5 miles.

During the 1999-2003 analysis period, approximately 16 percent of fatal and injury crashes on the U.S. and State highways occurred on the analysis segments. The segments also accounted for 18 percent of fatal or severe injury (K+A) crashes during the five year period.

Insert Table 5

Figure 4 shows the crash distribution by facility type for Fatal plus A-Injury crashes on the selected high crash segments. The crash type distribution for the selected segments (Top 5% Segments) is similar to the crash distribution for all segments based on classified facility type as shown in Figure 3.

Figure 4: Crash Severity by Roadway Type for Selected Segments (1999 to 2003)

Crash Type Analysis

Figure 4A depicts an example frequency distribution of sites for one ADT and roadway type class. The Appendix contains frequency distribution plots and pie charts describing the characteristics of crash types for each of the mileage and ADT classes. This information is essential to understanding the types and effectiveness of countermeasures. Some general findings from a review of this information are as follows:

· The crash rate (crashes per mile) is least on 2-lane rural roads, but a crash occurring on a 2-lane rural road is most likely to be severe - approximately 30% of 2-lane rural road crashes, other than property damage only, result in a fatality or A-type injury.

· More than one-half (approximately 53%) of fatal crashes occurred on a 2-lane rural roadway, predominantly those in the lower ADT classes.

· Urban multi-lane roadways make up only approximately 13% of the U.S. and State roadways (excluding freeways), but account for 28% of fatal crashes and 42% of 'A-type' injury crashes.

· Lower volume roadways experience a predominance of run-off-road (fixed object, overturn, etc.) crashes than any other crash type. Addressing the quality of the roadside will be the focus for such locations.

· In the urban environment the types of crashes that predominate include multi-vehicle (rear-end, angle and turning), and pedestrian. The multi-vehicle crashes are typically associated with access or driveway and intersection activities.

Figure 4A: Example of Crash Frequency Distribution used in Selection of High Risk Sample

There are many very short (1 to 3-mile) and isolated segments identified by this study throughout the state. At this level of analysis it is not possible to definitively ascribe a reasonable (i.e., effective) solution for many of these. In some cases spot improvements such as removal of fixed objects, treatment of sharp curves or other solutions may be appropriate. However, in others once field reviews are undertaken it may not be evident that any solution is appropriate.

District Summaries of High Risk Segments

All the segments identified were plotted on GIS maps of Illinois. The information was organized at the District level. The Appendix shows a statewide plot of the '5%' sample of high risk roadway segments; and also contains separate plots of high risk segments for each of IDOT's 9 districts. The intent is for each District to review these plots and undertake an evaluation of the feasibility and appropriate treatment for their selected high risk sites.

Clusters of High Risk Segments

The GIS plots of all identified high risk segments were prepared and reviewed. It became apparent that there were a number of roadways throughout the state with repeated high-crash segments adjacent or in close proximity to each other.

A total of 22 'high-risk roadway corridors' were thus identified for further study. These were defined as lengths of continuous roadway containing multiple, closely proximate or adjacent individual segments that were identified as high risk outliers. In some cases such corridors include four or more separate high crash segments; and in some cases these segments represented different ADT and/or roadway type classes

These 22 corridors are shown on Figure 5 and summarized in Table 6. These corridors may be of special interest in that a more comprehensive approach (e.g., reconstruction, multiple countermeasures) than spot treatment of a countermeasure is appropriate. We understand that some states are preparing reports to FHWA defining 'high-risk' corridors as their input to this required reporting. These 22 corridors may be considered equivalent to that effort. Note that the total mileage of these corridors represents 2.2% of mileage studied.

Insert Figure 5

Table 6: High Risk Roadway Corridors

Route	County (s)	IDOT District	Length (Miles)	Number of Fatal Crashes	Crash type
IL 109	Jersey	8	7.1	3	FO, OVT, AN
IL 15	Washington	8	10.8	6	FO, OVT
IL 156	Monroe	8	12.2	2	FO, OVT
IL 157	St. Clair	8	5.9	3	AG, T, RE, SDS, HO, ODS
IL 161	Marion, Clinton	8	4.9	1	RE, SDS, AG, T
IL 75	Winnebago	2	11.2	1	FO, OVT
IL 19	Cook	1	8.9	5	RE, SDS, AG, T, PD, PCL
IL 26	Woodford	4	11.4	2	AG, T, FO, OVT
IL 64	Cook	1	8.1	3	PD, PCL, AG, T,
IL 71	LaSalle	3	26.6	7	FO, OVT, AG, T
IL 84	Jo Daviess, Carrol	2	15.4	2	FO, OVT
IL 96	Pike	6	18.1	4	FO, OVT, HO, ODS
U.S. 14	McHenry	1	10.9	2	FO, OVT, HO, ODS
U.S. 24	Adams	6	7.0	1	FO, OVT
U.S. 30	Will	1	5.3	0	RE, SDS, AG, T
U.S. 41	Cook	1	7.2	9	RE, SDS, FO, OVT
U.S. 45	Cook	1	6.1	8	RE, SDS, PD, PCL,AG, T
U.S. 45	Johnson, Saline	9	25.1	3	FO, OVT, AG, T, RE, SDS
U.S. 45/52	Kankakee, Iroquois	3	13.1	3	FO, OVT, AG, T
IL 267	Greene	8	8.2	1	FO, OVT, RE, SDS, AG, T
IL 43	Cook	1	6.6	3	AG, T, RE, SDS
IL 50	Cook	1	8.1	10	PD, PCL, RE, SDS

FO: Fixed object, OVT: Overturned, AN: Animal, AG: Angle, T: Turning, RE: Rear-end, SDS: Same direction sideswipe, HO: Head-on, ODS: Opposite direction sideswipe, PD: Pedestrian, PCL: Pedalcyclist,

The Appendix contains datasheets with aerial photography and crash type data for each of these 22 corridors.

Other Evaluations

In addition to the segmentation analysis described above, CH2M HILL conducted separate studies of the database to uncover additional insights and provide focus for safety efforts going forward. These studies were intended to help overcome some of the limitations of the database noted above; i.e., the lack of geo-referenced information on off-system safety.

Off System Study

The off-system study addressed safety on the local roadway system in Illinois. Because crash records were not geo-coded for these types of roadways during the five-year analysis period, the analysis was conducted on an aggregate level, county-wide basis. The purpose was to identify outlier counties with the highest crash frequencies based on travel exposure for the five year (1999-2003) analysis period. A value for 'crashes per million vehicle miles traveled' (the most appropriate systemwide metric) was calculated for every county to determine relative system safety performance. Figure 6 shows counties from lowest to highest fatal and all injury crashes per million VMT and Figure 7 shows fatal and A-injury crashes per million VMT for the five year analysis period.
Insert Figure 6

Insert Figure 7

Cook and Peoria Counties have the highest overall rate of fatal plus injury crashes on the local roadway system. Districts 6 and 9 appear to contain the greatest concentration of counties with significantly higher overall crash rates. IDOT has begun to focus efforts with the counties in these Districts to advance safety programs on the local level. IDOT is working with local agencies to identify problem locations, to perform Road Safety Assessments, and to develop and fund integrated strategies. IDOT substantially increased HSIP and HRRR dollars to assist in the funding of safety improvements.

Interstate/Freeway Analysis

While this study did not address freeway crashes in total, a separate effort was made to look at the frequency of very severe median-related head-on crashes. This crash type has been found to be a significant and growing problem in many states, and countermeasures are being implemented to address such crashes.

Table 7 describes the crash severity and crash type for the Interstate system in Illinois from 1999-2003. More detailed analysis is needed to address specific corridors to address head-on and median crossover crashes. This effort will be undertaken for subsequent efforts in updating the Annual 5% Report in the future.

Table 7: Crash Severity and Crash Type Distribution on Interstates (1999-2003)

Interstates	Total Crashes (K+A+B+C)	Crash Severity		Crash type
Interstates	Total Crashes (K+A+B+C)	Fatal	A-injury	Fixed Object & Overturned	Head-On & Opposite Direction Sideswipe	Rear End & Same Direction Sideswipe	Angle & Turning	Animal	Pedestrian & Pedalcyclist	Others
I-24	112	1	35	64	1	19	6	13	1	8
I-39	477	19	93	256	7	111	39	31	1	32
I-55	5139	142	986	2020	75	2386	248	76	31	303
I-57	3643	151	792	1939	45	1066	203	112	15	263
I-64	801	28	165	409	16	240	45	35	2	54
I-70	574	33	157	357	13	112	27	29	2	34
I-72	456	15	113	211	3	81	27	93	4	37
I-74	1744	53	377	783	30	595	95	87	3	151
I-80	1936	73	426	915	42	684	108	20	13	154
I-88	1962	33	367	688	27	1031	101	33	12	70
I-90	3747	58	484	987	35	2374	183	19	23	126
I-94	9266	112	1054	2195	70	6206	484	7	41	263
I-155	84	3	20	57	0	10	2	8	1	6
I-172	34	1	6	20	1	1	1	7	0	4
I-180	29		6	13	0	1	1	13	0	1
I-190	242		22	40	5	155	30	0	6	6
I-255	282	12	69	144	6	79	20	4	1	28
I-270	229	9	58	93	6	96	14	4	1	15
I-280	36	1	4	22	1	8	1	0	1	3
I-290	3776	53	539	927	43	2453	189	1	35	128
I-294	3482	43	522	874	35	2216	208	2	28	119
I-355	793	13	147	284	11	413	50	0	6	29
I-474	119	2	33	51	2	30	8	10	2	16

Study of 'High Risk' Behaviors

Both the AASHTO Strategic Highway Safety Plan and Illinois' Comprehensive Safety Plan highlight the importance of addressing the full range of problems and solutions, including engineering, enforcement, education and emergency medical services. Cost effective application of resources to fully address identified problems suggests a similar approach to the roadway segmentation process.

To address these areas CH2M HILL characterized the distribution of 'high risk' behaviors on a county by county basis to determine geographic bias or tendencies, and provide focus for application of resources to address these behaviors.

Analyses were conducted by county of the following traffic safety behavioral features:

· Severe crashes in which the driver or occupant was unrestrained

· Severe crashes in which the driver was recorded as being impaired

· Severe crashes involving drivers 18 years old or younger

· Severe crashes involving drivers 70 years old or older

· Fatal motorcycle crashes wherein the driver was helmetless.

Unrestrained Drivers (See Figure 8) Counties that exhibited the highest percentage of unrestrained drivers or occupants involved in a fatal or severe injury crash were located predominantly in the southern portion of the State. The highest reported percentage was 67% in Edwards County. Average percentage of unrestrained drivers involved in fatal or severe injury crashes was 40%.

Counties with high percentages of unrestrained fatalities are candidates for targeted public education and enforcement programs.

Insert Figure 8

Impaired Drivers (also see Figure 8) Counties that exhibited the highest percentage of impaired drivers involved in fatal or severe injury crashes were also located predominantly in the southern portion of the State. Over the five years for which data were analyzed, only four counties were found to have impaired driver involvement significantly higher than the statewide average of 50%. Counties with high percentages of impaired driving fatalities are candidates for targeted enforcement programs.

One county appeared on both the unrestrained and impaired driver lists -- Greene County located in IDOT District 8 on the western edge of the State. This would appear to be a likely candidate for a targeted educational and enforcement program aimed at both increasing seat belt use and reducing the practice of driving while impaired. Consideration should also be given to a similar program in each of the other eight counties which appeared on only one of the lists of atypical high risk behavior.

Helmetless Motorcycle Fatalities (Also see Figure 8) The six-county Chicago metropolitan area accounted for approximately one-half of all helmetless motorcycle driver fatalities during the five-year period from 1999-2003. The number of fatalities per county (five years) ranged from 105 (Cook) to 14 (Will) compared with a statewide average of 3.76.

Young and Old Drivers (See Figure 9) Counties that exhibited the highest incidence of involvement in fatal or severe injury crashes by drivers 18 years old or younger; or drivers 70 years old and older are shown in Figure 9. There is no discernable locational pattern. Adams County on the Mississippi river at the western boundary of the State was high in both young and older driver categories. However, all of the counties identified in the Figure may be considered as candidates for a targeted educational program directed toward safer driving practices by young or older drivers, or both.

Insert Figure 9

Treating Top 5% Roadway Segments

Results of the selected segment analysis for non-freeway segments in the Illinois state data base are shown on a series of District maps contained in the Appendix. Approximately 6 percent of mileage was identified for the full range of roadway types and traffic volume ranges.

Data limitations discussed previously preclude definitive judgments or decisions regarding what should be done, if anything, at each location. Further study, including understanding fully site conditions (pavement and shoulder condition, roadside characteristics, right-of-way, etc.) is required.

It is the intention of IDOT to address each indicated location in the following manner:

1) It is first necessary to confirm that each location has not been materially changed or improved since 2003, the latest date of the crash database. Review of the exhibit and underlying information by each District is planned for the immediate future. Some segments may be removed from the map if it is determined they have been altered or reconstructed.

2) Analysis is limited to data contained in state crash, traffic and geometric data bases. Field review of these sites is needed to confirm the accuracy of the data, determine physically feasible engineering alternatives if any, and provide the necessary information to enable evaluation of the full range of appropriate countermeasures to each site. Additional effort to understand specifics of crash types (e.g., time of day, pavement or weather condition, etc.) is also necessary.

3) Updated crash information for 2004 and 2005 is expected within the next few months. This information will be used to confirm that these sites continue to be safety risks and to adjust the list or map accordingly.

4) Low cost safety improvements consistent with countermeasures discussed in the NCHRP Report 500 series and other recent research will be studied for each site. Authors of this report are serving as the program manager for development of the NCHRP Report 500 series documents and are fully aware of the contents. Effective countermeasures address the specific crash types that predominate at a site or can be expected given the type of roadway and level of traffic volume expected. Countermeasures have a cost both in dollar implementation terms and other factors of varying importance depending on the circumstances.

Countermeasures, Their Effectiveness, and Impediments to Their Implementation

Based on the literature, and specifically the NCHRP Report 500 series, the following is a series of countermeasures and their attributes for consideration at the high-risk roadway segments along with possible impediments to implementation of each countermeasure:

Table 8: Potential Countermeasures and Impediments to Implementation

2-Lane Rural Roadway
Low to Moderate Traffic Volume

Typical Predominant	Potential Countermeasure	Impediment to Implementation
Crash Types
Run off Road, Fixed Object and Overturned	Install shoulder/edgeline rumble strips	Requires paved shoulder in good condition
		Difficult snow removal
		Adverse effects on cyclists
		Undesirable noise levels
		Additional shoulder maintenance requirements
	Improve or provide delineation

	Remove/relocate roadside obstacles	Public reaction to tree cutting
		Coordination with environmental and public groups

	Implement guardrail	Potential widening and attendant impacts
		Additional maintenance requirements

	Pave shoulder; implement 'safety wedge'	Requires sufficient width of unpaved shoulder

	Flatten sideslope; reshape or regrade ditch	Potential right-of-way required
		Affect drainage patterns (culvert and other issues)
		Potential environmental issues re: Right-of-way

	Widen pavement/shoulder through curve	Potential Right-of-way required

	Improve superelevation transition

	Advance curve warning (sign, rumble strips, etc.)

	Reconstruct horizontal curve	Right-of-way required; more extensive impacts
		Generally cost-effective for only higher volumes

Table 8 Potential Countermeasures and Impediments to Implementation (continued)
2-Lane Rural Roadway
Low to Moderate Traffic Volume

Typical Predominant	Potential Countermeasure	Impediment to Implementation
Crash Types
Rear-End and Same Direction Sideswipe	Relocate or remove driveways/minor intersections	Property owner objections to changes in access

	Widen to provide left turn lane(s)	Potential right-of-way and environmental issues

	Enforce speed limit	Requires shoulder or other locations for enforcement
		Diverts resources from other enforcement activities

	Remove/relocate roadside sight obstructions	Public reaction to tree cutting

	Improve vertical geometry to enhance sight distance	Potential/probable right-of-way required

Table 8 Potential Countermeasures and Impediments to Implementation (continued)
2-Lane Rural Roadway
High Traffic Volume

Typical Predominant	Potential Countermeasure	Impediment to Implementation
Crash Types
Rear-End and Same Direction Sideswipe	Relocate or remove driveways/minor intersections	Property owner objections to changes in access

	Widen or place in median left turn lane(s)	Potential right-of-way and environmental issues

	Enforce speed limit	Requires shoulder or other locations for enforcement
		Diverts resources from other enforcement activities

	Improve advance warning of signals, intersections
Fixed Object and Overturned	Install shoulder/edgeline rumble strips	Requires paved shoulder in good condition
		Difficult snow removal
		Adverse effects on cyclists
		Undesirable noise levels
		Additional shoulder maintenance requirements

	Remove/relocate roadside obstacles	Public reaction to tree cutting
		Coordination with environmental and public groups

	Implement guardrail	Potential widening and attendant impacts
		Additional maintenance requirements

	Pave shoulder; implement 'safety wedge'	Requires sufficient width of unpaved shoulder

	Flatten sideslope; reshape or regrade ditch	Potential right-of-way required
		Affect drainage patterns (culvert and other issues)
		Potential environmental issues re: Right-of-way
		Adverse effects on cyclists
		Undesirable noise levels

Table 8 Potential Countermeasures and Impediments to Implementation (continued)
Multi-Lane Rural Roadway

Typical Predominant	Potential Countermeasure	Impediment to Implementation
Crash Types
Rear-End and Same Direction Sideswipe	Enforce speed limit	Diverts resources from other enforcement activities

	Provide left turn lane(s)	Potential right-of-way and environmental issues
		Affects median drainage

	Remove roadside sight obstructions	Public reaction to tree cutting
		Coordination with environmental and public groups

Fixed Object and Overturned	Install shoulder/edgeline rumble strips	Difficult snow removal
		Adverse effects on cyclists
		Undesirable noise levels
		Additional shoulder maintenance requirements

	Remove/relocate roadside obstacles	Public reaction to tree cutting
		Coordination with environmental and public groups

Table 8 Potential Countermeasures and Impediments to Implementation (continued)
Urban Arterials

Typical Predominant	Potential Countermeasure	Impediment to Implementation
Crash Types
Rear-end and same direction sideswipe	Add left turn lanes	Limited space may preclude or require right-of-way
		Proximity to major intersection may limit ability

	Implement median access control (raised)	Objections of adjacent property owners (access)
		Affect drainage patterns
		Increase maintenance requirements

	Relocate/close driveways	Objections of adjacent property owners (access)

	Improve or establish progression for signals	Conflicts with signal requirements of crossing roads
		Requires consensus of neighboring towns
	Restrict or prohibit left turns	Increases out of direction travel
		Objections of adjacent property owners (access)

Pedestrian	Add/improve signalization along arterial for peds	May degrade operational quality

	Implement raised median	Objections of adjacent property owners (access)
		Affect drainage patterns
		Increase maintenance requirements

	Revise and enforce speed limits	Requires shoulder or other locations for enforcement
		Diverts resources from other enforcement activities

Table 8 Potential Countermeasures and Impediments to Implementation (continued)
Urban Arterials

Typical Predominant	Potential Countermeasure	Impediment to Implementation
Crash Types
Angle and Turning	Add left turn lanes	Limited space may preclude or require right-of-way
		Proximity to major intersection may limit ability

	Implement median access control (raised)	Objections of adjacent property owners (access)

		Affect drainage patterns
		Increase maintenance requirements

	Relocate/close driveways	Objections of adjacent property owners (access)

	Restrict or prohibit left turns	Increases out of direction travel
		Objections of adjacent property owners (access)

Obtaining the maximum value for the effort and resources expended requires consideration of the cost-effectiveness of prioritizing a location and selecting the appropriate countermeasure. Prioritization does not necessarily mean that the highest volume or highest frequency locations are addressed first. The cost and/or difficulty of implementation at one site may make it less of a priority than a lower volume site with fewer crashes for which a countermeasure can be readily implemented.

CH2M HILL suggests development of a simple 'cost per crash eliminated' metric as a means of prioritizing and ultimately implementing countermeasures. This approach is similar to that taken in development of TRB Special Report 214, Designing Safer Roads, Practices for Resurfacing, Restoration and Rehabilitation, 1987. In that document the researchers asserted that measures with a cost per crash eliminated of less than $10,000 were clearly appropriate on safety reasons alone; where the cost per crash eliminated was from $10,000 to $50,000 the cost-effectiveness may depend on other factors; and where the cost per crash eliminated exceeded $50,000 it would generally not be cost effective.

An analysis of the cost per crash eliminated for the selected sites was prepared to determine the range of cost effectiveness. Values for expected countermeasure effectiveness were taken from NCHRP Report 500 series documents as well as information from Minnesota's state strategic plan evaluation tool (prepared for MnDOT by CH2M HILL). Nominal implementation costs for lower cost improvements were assigned. FHWA's Lane Departure Strategic Action Plan (March 2005) was referenced as well. The following general conclusions were drawn that can help direct site-specific implementation:

· For lower volume roadways (less than 2500 vpd) strategies that cost less than $5000 per mile will generally be preferred to maximize total system effectiveness. Such strategies will generally include implementation of rumble strips, pavement edge drop treatments, enhanced delineation of objects or edges of pavement; placing of warning signs, and other treatments that do not require geometric changes, right-of-way and other complications.

· For moderate to higher volume two-lane rural roadways, additional strategies such as removal of fixed objects, paving of shoulders, improved or enhanced guardrail that have a higher cost (on the order of $10,000 per mile) will be effective. Of course, should less costly treatments be as effective they should first be implemented.

· High volume rural roadways and urban arterials experience crash types that would tend to require more extensive treatments. Rear-end crashes associated with driveway and other access require widening for left turn lanes, which in turn involves environmental, drainage, right-of-way and other complications. The number of crashes affected is greater but so is both the cost and difficulty. A planning level threshold of $50,000 to $100,000 per mile may be cost-effective.

Site-specific analysis of implementation costs and expected long-term improvements should be conducted. Decisions should be made regarding prioritization and implementation of these improvements as part of each District's safety program. Where reconstruction or resurfacing/3R improvements are expected or programmed, selected safety improvements can and should be incorporated. Districts may wish to defer treatment of a 'high risk' site in the immediate future if it is programmed for construction in a few years. Coordination with local units of government, including specifically law enforcement, is recommended to obtain maximum value for invested dollar.

High Risk Corridors

This study also developed a list of 22 high risk corridors in which multiple high-risk segments in close proximity were evident. The suggested approach to these corridors is to undertake a more comprehensive study to determine the appropriate approach. Rather than spot treatment with selected countermeasures, it may be appropriate to consider reconstruction (alignment revisions, cross section improvements, etc.) over the length of these corridors. Note that the types of safety problems and measures to address them may vary significantly. In many cases it seems evident that the nature of the problem is related to access control, turning and intersection-related conflicts, and in the cases of the arterials in Cook County, pedestrian-related.

High Risk Behaviors

Counties in which there is evidence of significant overrepresentation of high risk behavior (alcohol, lack of seat belt usage, speeding) may be subjects for multi-agency efforts to combat these behaviors. Allocation of state funds to these specific counties may be the most cost-effective use of these limited funds. Targeted enforcement activities, targeted public information efforts, or some combination of these may prove effective.

Conclusion

This is the first year of the FHWA 5% reporting requirement; and with that, many states identified multiple challenges as they worked to complete this report and the other required safety program reports, especially given the time constraints of implementing the new federal safety program. IDOT faced some of these same challenges: the inability to locate crashes on the local roadway system, availability of current crash data, and ultimately, how the 5% roadways are identified.

Illinois developed and began its first year of implementation of its Comprehensive Highway Safety Plan (CHSP). Through this CHSP, IDOT is in the process of implementing several changes to better direct efforts towards reducing fatalities and serious injuries on all of Illinois' public roadways. Thus, this 5% report will be considered in the overall direction of IDOT's safety efforts but will not be the primary source directing its efforts for the upcoming year. One source the department will be using is based on a new initiative. Five years of fatal and serious injury crashes occurring on the state roadway system were located, identified by crash type, and placed on a GIS map. The state multi-year construction program is overlaid onto this map, allowing IDOT to better direct resources to safety improvements through regular programmed projects, maintenance forces, or the use of HSIP dollars.

The department has also directed additional resources towards the effort of improving the quality and timeliness of crash data, especially on the local roadway system. Several initiatives are ongoing at this point in time and include items such as expanding the use of electronic crash reports, assisting the local agencies financially to identify crash locations by geocode, and developing a Safety Data Mart system which will act as a data warehouse for both internal and external users and allow for various queries. These initiatives will drastically improve IDOT's ability to effectively identify problems, direct resources, create reports, further evaluate the effectiveness of projects and countermeasures in the future and ultimately, reduce fatalities and serious injuries on all Illinois public roadways.

To further optimize its efforts and maximize the benefit of safety improvements, IDOT revised its HSIP policy and developed a new benefit cost methodology that will focus on severe crashes. In addition, IDOT is pursuing developing safety performance functions that will direct efforts towards those roadways that are showing significant poor performance with respect to safety.

IDOT is committed to reducing fatalities and serious injuries on all Illinois roadways and will have many of its initiatives fully implemented this year, thus next year's reporting will better represent what IDOT considers as the 5% most severe safety needs for all public roadways.

^[1] IDOT classifies crash severity as follows:

. K Fatal - A fatal crash is a traffic crash involving a motor vehicle in which at least one person dies within 30 days of the crash.

. A Incapacitating injury - Any injury, other than a fatal injury, which prevents the injured person from walking, driving, or normally continuing the activities he/she was capable of performing before the injury occurred. Inclusions: severe lacerations, broken/distorted limbs, skull injuries, chest injuries and abdominal injuries.

. B Nonincapacitating injury - Any injury, other than a fatal or incapacitating injury, which is evident to observers at the scene of the crash. Inclusions: lumps on the head, abrasions, bruises, and minor lacerations.

. C Reported, not evident - Any injury reported or claimed which is not listed above. Inclusions: momentary unconsciousness, claims of injuries not evident, limping, complaints of pain, nausea.

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