Study Details

Study Title: Safety Impacts of Highway Shoulder Attributes in Illinois

Authors: Bamzai et al.

Publication Date: APR, 2011

Abstract: The single greatest category of highway vehicle crashes is run-off-the-road incidents. Significant material differences and elevation changes in shoulder edges pose a potential safety hazard when a vehicle leaves the travel way. Shoulder paving is recognized as a positive countermeasure to reduce a shoulder drop-off hazard. This report documents an in-depth analysis of safety impacts of shoulder attributes using data on Illinois state maintained highways for period 2000-2006. Preliminary data analysis is first conducted to establish the correlation between shoulder-related crashes by type and severity category and shoulder attributes such as shoulder material type and outside paved shoulder width. Then, an analytical procedure is developed and applied to the Illinois data for assessing safety impacts of shoulder paving and prioritizing highway segments for shoulder paving using the Empirical Bayesian (EB) analysis and cross-sectional analysis approaches and an optimization model. While this procedure does not eliminate the need for human judgment, it could help experts make better decisions using optimization techniques. The findings are expected to help Illinois Department of Transportation (DOT) update current design manuals.

Study Citation: Bamzai, R., Y. Lee, and Z. Li. "Safety Impacts of Highway Shoulder Attributes in Illinois." Report No. FHWA-ICT-11-078. Illinois Department of Transportation. Springfield, Illinois. (April 2011).

Related Citations: Li, Z., K. Kepaptsoglou, Y. Lee, H. Patel, Y. Liu, and H.G. Kim. "Safety Effects of Shoulder Paving for Rural and Urban Interstate, Multilane, and Two-Lane Highways". Journal of Transportation Engineering, Vol. 139, (2013) pp 1010-1019.

Study Report: Download the Study Report Document


CMFs Associated With This Study

Category: Shoulder treatments

Countermeasure: Add new paved shoulder

CMF CRF(%) Quality Crash Type Crash Severity Roadway Type Area Type
0.57 43 3 Stars Fixed object,Head on,Run off road,Sideswipe K Not specified Urban
1.02 -2 3 Stars Fixed object,Head on,Run off road,Sideswipe A,B,C Not specified Urban
0.25 75 3 Stars Fixed object,Head on,Run off road,Sideswipe O Not specified Urban
0.6 40 3 Stars Fixed object,Head on,Run off road,Sideswipe K Not specified Urban
0.33 67 3 Stars Fixed object,Head on,Run off road,Sideswipe A,B,C Not specified Urban
0.51 49 3 Stars Fixed object,Head on,Run off road,Sideswipe O Not specified Urban
0.57 43 3 Stars Fixed object,Head on,Run off road,Sideswipe K Not specified Urban
0.97 3 3 Stars Fixed object,Head on,Run off road,Sideswipe A,B,C Not specified Urban
0.25 75 3 Stars Fixed object,Head on,Run off road,Sideswipe O Not specified Urban
0.91 9 3 Stars Fixed object,Head on,Run off road,Sideswipe K Not specified Urban
0.79 21 3 Stars Fixed object,Head on,Run off road,Sideswipe A,B,C Not specified Urban
0.96 4 3 Stars Fixed object,Head on,Run off road,Sideswipe O Not specified Urban
0.66 34 3 Stars Fixed object,Head on,Run off road,Sideswipe K Not specified Urban
0.86 14 3 Stars Fixed object,Head on,Run off road,Sideswipe A,B,C Not specified Urban
0.4 60 3 Stars Fixed object,Head on,Run off road,Sideswipe O Not specified Urban
0.98 2 3 Stars Fixed object,Head on,Run off road,Sideswipe K Not specified Urban
0.72 28 3 Stars Fixed object,Head on,Run off road,Sideswipe A,B,C Not specified Urban
0.89 11 3 Stars Fixed object,Head on,Run off road,Sideswipe O Not specified Urban
0.67 33 3 Stars Fixed object,Head on,Run off road,Sideswipe K Not specified Urban
0.85 15 3 Stars Fixed object,Head on,Run off road,Sideswipe A,B,C Not specified Urban
0.41 59 3 Stars Fixed object,Head on,Run off road,Sideswipe O Not specified Urban
0.7 30 3 Stars Fixed object,Head on,Run off road,Sideswipe K Not specified Urban
0.36 64 3 Stars Fixed object,Head on,Run off road,Sideswipe A,B,C Not specified Urban
0.69 31 3 Stars Fixed object,Head on,Run off road,Sideswipe O Not specified Urban
1.17 -17 3 Stars Fixed object,Head on,Run off road,Sideswipe K Not specified Urban
0.98 2 3 Stars Fixed object,Head on,Run off road,Sideswipe A,B,C Not specified Urban
1.07 -7 3 Stars Fixed object,Head on,Run off road,Sideswipe O Not specified Urban
0.68 32 3 Stars Fixed object,Head on,Run off road,Sideswipe K Not specified Urban
0.97 3 3 Stars Fixed object,Head on,Run off road,Sideswipe A,B,C Not specified Urban
0.41 59 3 Stars Fixed object,Head on,Run off road,Sideswipe O Not specified Urban
0.94 6 3 Stars Fixed object,Head on,Run off road,Sideswipe K Not specified Urban
0.72 28 3 Stars Fixed object,Head on,Run off road,Sideswipe A,B,C Not specified Urban
0.88 12 3 Stars Fixed object,Head on,Run off road,Sideswipe O Not specified Urban
1.58 -58 3 Stars Fixed object,Head on,Run off road,Sideswipe K Not specified Urban
1.62 -62 3 Stars Fixed object,Head on,Run off road,Sideswipe A,B,C Not specified Urban
1.65 -65 3 Stars Fixed object,Head on,Run off road,Sideswipe O Not specified Urban

Countermeasure: Pave shoulder

CMF CRF(%) Quality Crash Type Crash Severity Roadway Type Area Type
0.77 23 3 Stars Fixed object,Head on,Run off road,Sideswipe K Principal Arterial Interstate Rural
0.9 10 4 Stars Fixed object,Head on,Run off road,Sideswipe A,B,C Principal Arterial Interstate Rural
0.99 1 4 Stars Fixed object,Head on,Run off road,Sideswipe O Principal Arterial Interstate Rural
0.41 59 3 Stars Fixed object,Head on,Run off road,Sideswipe K Not specified Rural
0.32 68 3 Stars Fixed object,Head on,Run off road,Sideswipe A,B,C Not specified Rural
0.48 52 3 Stars Fixed object,Head on,Run off road,Sideswipe O Not specified Rural
0.82 18 3 Stars Fixed object,Head on,Run off road,Sideswipe K Not specified Rural
0.82 18 4 Stars Fixed object,Head on,Run off road,Sideswipe A,B,C Not specified Rural
0.75 25 4 Stars Fixed object,Head on,Run off road,Sideswipe O Not specified Rural
0.98 2 3 Stars Fixed object,Head on,Run off road,Sideswipe K Principal Arterial Interstate Urban
0.81 19 4 Stars Fixed object,Head on,Run off road,Sideswipe A,B,C Principal Arterial Interstate Urban
0.96 4 4 Stars Fixed object,Head on,Run off road,Sideswipe O Principal Arterial Interstate Urban
0.65 35 3 Stars Fixed object,Head on,Run off road,Sideswipe K Not specified Urban
0.24 76 3 Stars Fixed object,Head on,Run off road,Sideswipe A,B,C Not specified Urban
0.23 77 4 Stars Fixed object,Head on,Run off road,Sideswipe O Not specified Urban
0.91 9 3 Stars Fixed object,Head on,Run off road,Sideswipe K Not specified Urban
0.93 7 3 Stars Fixed object,Head on,Run off road,Sideswipe A,B,C Not specified Urban
0.85 15 3 Stars Fixed object,Head on,Run off road,Sideswipe O Not specified Urban
0.99 1 3 Stars Fixed object,Head on,Run off road,Sideswipe K Not specified Rural
0.97 3 3 Stars Fixed object,Head on,Run off road,Sideswipe A,B,C Not specified Rural
0.93 7 3 Stars Fixed object,Head on,Run off road,Sideswipe O Not specified Rural
0.86 14 3 Stars Fixed object,Head on,Run off road,Sideswipe K Principal Arterial Interstate Urban
0.86 14 3 Stars Fixed object,Head on,Run off road,Sideswipe A,B,C Principal Arterial Interstate Urban
1.35 -35 3 Stars Fixed object,Head on,Run off road,Sideswipe O Principal Arterial Interstate Urban
0.9 10 3 Stars Fixed object,Head on,Run off road,Sideswipe K Not specified Urban
0.93 7 3 Stars Fixed object,Head on,Run off road,Sideswipe A,B,C Not specified Urban
0.85 15 3 Stars Fixed object,Head on,Run off road,Sideswipe O Not specified Urban
1.28 -28 3 Stars Fixed object,Head on,Run off road,Sideswipe K Principal Arterial Interstate Rural
1.08 -8 3 Stars Fixed object,Head on,Run off road,Sideswipe A,B,C Principal Arterial Interstate Rural
1.14 -14 4 Stars Fixed object,Head on,Run off road,Sideswipe O Principal Arterial Interstate Rural
1.21 -21 3 Stars Fixed object,Head on,Run off road,Sideswipe K Not specified Rural
1.44 -44 3 Stars Fixed object,Head on,Run off road,Sideswipe A,B,C Not specified Rural
1.35 -35 3 Stars Fixed object,Head on,Run off road,Sideswipe O Not specified Rural
0.99 1 3 Stars Fixed object,Head on,Run off road,Sideswipe K Not specified Rural
0.94 6 3 Stars Fixed object,Head on,Run off road,Sideswipe A,B,C Not specified Rural
0.93 7 3 Stars Fixed object,Head on,Run off road,Sideswipe O Not specified Rural
1.1 -10 3 Stars Fixed object,Head on,Run off road,Sideswipe K Not specified Rural
0.98 2 4 Stars Fixed object,Head on,Run off road,Sideswipe A,B,C Not specified Rural
1.04 -4 4 Stars Fixed object,Head on,Run off road,Sideswipe O Not specified Rural
1.23 -23 3 Stars Fixed object,Head on,Run off road,Sideswipe K Principal Arterial Interstate Urban
1.22 -22 4 Stars Fixed object,Head on,Run off road,Sideswipe A,B,C Principal Arterial Interstate Urban
1.26 -26 4 Stars Fixed object,Head on,Run off road,Sideswipe O Principal Arterial Interstate Urban
1.02 -2 3 Stars Fixed object,Head on,Run off road,Sideswipe K Not specified Urban
1.06 -6 3 Stars Fixed object,Head on,Run off road,Sideswipe A,B,C Not specified Urban
1.14 -14 4 Stars Fixed object,Head on,Run off road,Sideswipe O Not specified Urban
1.14 -14 3 Stars Fixed object,Head on,Run off road,Sideswipe K Not specified Urban
0.94 6 3 Stars Fixed object,Head on,Run off road,Sideswipe A,B,C Not specified Urban
1.17 -17 3 Stars Fixed object,Head on,Run off road,Sideswipe O Not specified Urban
0.76 24 3 Stars Fixed object,Head on,Run off road,Sideswipe K Principal Arterial Interstate Rural
0.95 5 3 Stars Fixed object,Head on,Run off road,Sideswipe A,B,C Principal Arterial Interstate Rural
0.87 13 3 Stars Fixed object,Head on,Run off road,Sideswipe O Principal Arterial Interstate Rural
1.17 -17 3 Stars Fixed object,Head on,Run off road,Sideswipe K Not specified Rural
1.48 -48 3 Stars Fixed object,Head on,Run off road,Sideswipe A,B,C Not specified Rural
1.16 -16 3 Stars Fixed object,Head on,Run off road,Sideswipe O Not specified Rural
1.17 -17 3 Stars Fixed object,Head on,Run off road,Sideswipe K Not specified Rural
1.13 -13 3 Stars Fixed object,Head on,Run off road,Sideswipe A,B,C Not specified Rural
1.23 -23 3 Stars Fixed object,Head on,Run off road,Sideswipe O Not specified Rural
1.24 -24 3 Stars Fixed object,Head on,Run off road,Sideswipe K Principal Arterial Interstate Urban
1.21 -21 3 Stars Fixed object,Head on,Run off road,Sideswipe A,B,C Principal Arterial Interstate Urban
1.26 -26 3 Stars Fixed object,Head on,Run off road,Sideswipe O Principal Arterial Interstate Urban
0.97 3 3 Stars Fixed object,Head on,Run off road,Sideswipe K Not specified Urban
0.98 2 3 Stars Fixed object,Head on,Run off road,Sideswipe A,B,C Not specified Urban
0.84 16 3 Stars Fixed object,Head on,Run off road,Sideswipe O Not specified Urban
0.83 17 3 Stars Fixed object,Head on,Run off road,Sideswipe K Not specified Urban
0.94 6 3 Stars Fixed object,Head on,Run off road,Sideswipe A,B,C Not specified Urban
0.76 24 3 Stars Fixed object,Head on,Run off road,Sideswipe O Not specified Urban
1.09 -9 3 Stars Fixed object,Head on,Run off road,Sideswipe K Not specified Urban
1.37 -37 3 Stars Fixed object,Head on,Run off road,Sideswipe A,B,C Not specified Urban
1.07 -7 3 Stars Fixed object,Head on,Run off road,Sideswipe O Not specified Urban
1.24 -24 3 Stars Fixed object,Head on,Run off road,Sideswipe K Principal Arterial Interstate Rural
1.1 -10 3 Stars Fixed object,Head on,Run off road,Sideswipe A,B,C Principal Arterial Interstate Rural
1.14 -14 3 Stars Fixed object,Head on,Run off road,Sideswipe O Principal Arterial Interstate Rural
1.02 -2 3 Stars Fixed object,Head on,Run off road,Sideswipe K Not specified Rural
1.31 -31 3 Stars Fixed object,Head on,Run off road,Sideswipe A,B,C Not specified Rural
1.1 -10 3 Stars Fixed object,Head on,Run off road,Sideswipe O Not specified Rural
0.95 5 3 Stars Fixed object,Head on,Run off road,Sideswipe K Not specified Rural
0.84 16 3 Stars Fixed object,Head on,Run off road,Sideswipe A,B,C Not specified Rural
0.85 15 3 Stars Fixed object,Head on,Run off road,Sideswipe O Not specified Rural
1.1 -10 3 Stars Fixed object,Head on,Run off road,Sideswipe K Not specified Rural
0.97 3 3 Stars Fixed object,Head on,Run off road,Sideswipe A,B,C Not specified Rural
0.98 2 3 Stars Fixed object,Head on,Run off road,Sideswipe O Not specified Rural
1.21 -21 3 Stars Fixed object,Head on,Run off road,Sideswipe K Principal Arterial Interstate Urban
1.27 -27 3 Stars Fixed object,Head on,Run off road,Sideswipe A,B,C Principal Arterial Interstate Urban
1.28 -28 3 Stars Fixed object,Head on,Run off road,Sideswipe O Principal Arterial Interstate Urban
1.04 -4 3 Stars Fixed object,Head on,Run off road,Sideswipe K Not specified Urban
0.79 21 3 Stars Fixed object,Head on,Run off road,Sideswipe A,B,C Not specified Urban
1.14 -14 3 Stars Fixed object,Head on,Run off road,Sideswipe O Not specified Urban
1.12 -12 3 Stars Fixed object,Head on,Run off road,Sideswipe K Not specified Urban
0.81 19 3 Stars Fixed object,Head on,Run off road,Sideswipe A,B,C Not specified Urban
1.11 -11 3 Stars Fixed object,Head on,Run off road,Sideswipe O Not specified Urban

Countermeasure: Widen shoulder

CMF CRF(%) Quality Crash Type Crash Severity Roadway Type Area Type
0.96 4 3 Stars Fixed object,Head on,Run off road,Sideswipe K Principal Arterial Interstate Rural
0.99 1 3 Stars Fixed object,Head on,Run off road,Sideswipe A,B,C Principal Arterial Interstate Rural
0.67 33 4 Stars Fixed object,Head on,Run off road,Sideswipe O Principal Arterial Interstate Rural
0.81 19 3 Stars Fixed object,Head on,Run off road,Sideswipe K Principal Arterial Interstate Urban
0.74 26 3 Stars Fixed object,Head on,Run off road,Sideswipe A,B,C Principal Arterial Interstate Urban
0.83 17 4 Stars Fixed object,Head on,Run off road,Sideswipe O Principal Arterial Interstate Urban
0.77 23 3 Stars Fixed object,Head on,Run off road,Sideswipe K Principal Arterial Interstate Urban
0.64 36 3 Stars Fixed object,Head on,Run off road,Sideswipe A,B,C Principal Arterial Interstate Urban
0.85 15 3 Stars Fixed object,Head on,Run off road,Sideswipe O Principal Arterial Interstate Urban
0.69 31 3 Stars Fixed object,Head on,Run off road,Sideswipe K Not specified Urban
0.66 34 3 Stars Fixed object,Head on,Run off road,Sideswipe A,B,C Not specified Urban
0.45 55 3 Stars Fixed object,Head on,Run off road,Sideswipe O Not specified Urban
1.19 -19 3 Stars Fixed object,Head on,Run off road,Sideswipe K Principal Arterial Interstate Rural
1.35 -35 3 Stars Fixed object,Head on,Run off road,Sideswipe A,B,C Principal Arterial Interstate Rural
0.95 5 3 Stars Fixed object,Head on,Run off road,Sideswipe O Principal Arterial Interstate Rural
0.96 4 3 Stars Fixed object,Head on,Run off road,Sideswipe K Principal Arterial Interstate Urban
0.76 24 3 Stars Fixed object,Head on,Run off road,Sideswipe A,B,C Principal Arterial Interstate Urban
1.06 -6 4 Stars Fixed object,Head on,Run off road,Sideswipe O Principal Arterial Interstate Urban
0.95 5 3 Stars Fixed object,Head on,Run off road,Sideswipe K Principal Arterial Interstate Rural
0.94 6 3 Stars Fixed object,Head on,Run off road,Sideswipe A,B,C Principal Arterial Interstate Rural
0.76 24 3 Stars Fixed object,Head on,Run off road,Sideswipe O Principal Arterial Interstate Rural
0.83 17 3 Stars Fixed object,Head on,Run off road,Sideswipe K Principal Arterial Interstate Urban
0.72 28 3 Stars Fixed object,Head on,Run off road,Sideswipe A,B,C Principal Arterial Interstate Urban
0.48 52 3 Stars Fixed object,Head on,Run off road,Sideswipe O Principal Arterial Interstate Urban
1.22 -22 3 Stars Fixed object,Head on,Run off road,Sideswipe K Principal Arterial Interstate Rural
1.51 -51 3 Stars Fixed object,Head on,Run off road,Sideswipe A,B,C Principal Arterial Interstate Rural
0.98 2 3 Stars Fixed object,Head on,Run off road,Sideswipe O Principal Arterial Interstate Rural
1.02 -2 3 Stars Fixed object,Head on,Run off road,Sideswipe K Principal Arterial Interstate Urban
0.81 19 3 Stars Fixed object,Head on,Run off road,Sideswipe A,B,C Principal Arterial Interstate Urban
1.09 -9 3 Stars Fixed object,Head on,Run off road,Sideswipe O Principal Arterial Interstate Urban
0.9 10 3 Stars Fixed object,Head on,Run off road,Sideswipe K Not specified Urban
0.64 36 3 Stars Fixed object,Head on,Run off road,Sideswipe A,B,C Not specified Urban
0.49 51 3 Stars Fixed object,Head on,Run off road,Sideswipe O Not specified Urban