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Turner-Fairbank Highway Research Center


HSIS Summaries

HSIS Summary Reports are two to eight pages in length and include a brief description of the issue addressed, data used, methodology applied, significant results, and practical implications.

Title Pub Date Author Report Number
Accident Analysis of Older Drivers at Intersections Feb-95 FHWA-RD-94-021
Accident Relationships of Roadway Widths on Low-Volume Roads Jun-94 Charles V. Zegeer FHWA-RD-94-023
An Examination of Fault, Unsafe Driving Acts, and Total Harm in Car-Truck Collisions Jun-04 Council, F.M., D.L. Harkey, D.T. Nabors, A.J. Khattak, and Y.M. Mohamedshah FHWA-HRT-04-085
Analysis of Commercial Bus Crashes Nov-92 Charles V. Zegeer (HSRC) FHWA-RD-93-018
Analysis of Older Drivers On Freeways Aug-96 David L. Harkey, Herman Huang, and Charles V. Zegeer FHWA-RD-96-035
Association of Selected Intersection Factors with Red-Light-Running Crashes May-00 Yusuf M. Mohamedshah, Li Wan Chen, and Forrest M. Council FHWA-RD-00-112
Comparison of the Safety of Lighting Options on Urban Freeway May-95 Michael S. Griffith FHWA-RD-94-188
Development of a Speeding-Related Crash Typology May-10 Council, F.M., R. Srinivasan, S. Masten, D. Carter, and M. Reurings FHWA-HRT-10-039
Effects of a Towaway Reporting Threshold on Crash Analysis Results Aug-98 Charles V. Zegeer, Herman F. Huang, J. Richard Stewart, Ron Pfefer, Jun Wang FHWA-RD-98-114
Evaluation of Lane Reduction "Road Diet" Measures on Crashes Jun-10 Persaud, B. and C. Lyon FHWA-HRT-10-053
Factors Contributing to Pedestrian and Bicycle Crashes on Rural Highways Jun-10 Carter, D. and F. Council FHWA-HRT-10-052
GIS-Based Crash Referencing and Analysis System Feb-99 David L. Harkey FHWA-RD-99-081
Investigation of Crashes with Animals Mar-95 Warren E. Hughes and Reza Saremi FHWA-RD-94-156
Investigation of Highway Work Zone Crashes: What We Know and What We Don't Know Oct-96 Jun Wang, Warren E. Hughes, Forrest M. Council, and Jeffrey F. Paniati FHWA-RD-96-100
Investigation of National Highway System Roadways in the HSIS States Apr-98 Charles V. Zegeer, Herman F. Huang, J. Richard Stewart, and Carolyn Williams FHWA-RD-98-080
Review of the Impacts of the Towaway Reporting Threshold on a Highway Safety Program Jul-01 Lacy, K., C. Zegeer, and R. Schneider FHWA-RD-01-114
Safety Effects of Cross-Section Design on Rural Multilane Highways Jun-97 Jun Wang, Warren E. Hughes, and Richard Stewart FHWA-RD-97-027
Safety Effects of Horizontal Curve and Grade Combinations on Rural Two-Lane Highways Jan-14 FHWA-HRT-13-078
Safety Effects of the Conversion of Rural Two-Lane Roadways to Four-Lane Roadways Nov-99 Forrest M. Council and J. Richard Stewart FHWA-RD-99-206
Safety Effects of Using Narrow Lanes and Shoulder-Use Lanes to Increase the Capacity of Urban Freeways Jun-05 Bauer, K.M., D.W. Harwood, K.R. Richard, and W.E. Hughes FHWA-HRT-05-001

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Safety Effects of Horizontal Curve and Grade Combinations on Rural Two-Lane Highways

The safety effects of horizontal curves and grades on rural two-lane highways have been quantified in the American Association of State Highway and Transportation Officials (AASHTO) Highway Safety Manual (HSM), but it was not previously known whether and how the safety performance of horizontal curves and grades interact. Furthermore, there are no established safety effects for crest and sag vertical curves, and it is unknown whether and how the safety performance of crest or sag vertical curves is affected by the presence of horizontal curves.

The objective of this study was to quantify the combined safety effects of horizontal curves and grade combinations and express the results as crash modification factors (CMFs) that can be considered for use in the AASHTO HSM.

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Safety Evaluation of Converting Traffic Signals from Incandescent to Light-Emitting Diodes

Across the Nation, many agencies have been replacing conventional incandescent light bulbs in traffic signals with light-emitting diodes (LED). LEDs are primarily installed to reduce energy consumption and decrease maintenance. In addition, LEDs are expected to last much longer compared with incandescent bulbs and tend to age gradually. However, a recent study revealed several potential problems with LEDs, including their inability to melt snow and issues related to visual discomfort caused by glare at night.

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Safety Evaluation Of Discontinuing Late-Night Flash Operations at Signalized Intersections

During late-night flash (LNF) mode (from late night to early morning hours), traffic signals flash yellow for one road (typically, the major road), requiring caution but no stopping, and flash red for the other road (typically, the minor road), requiring drivers to stop and then proceed through the intersection after yielding to the traffic on the major road. The intent of LNF is to reduce energy consumption and delay during periods of low traffic demand. However, in recent years, many agencies have begun replacing LNF with normal phasing operation because of safety concerns.

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