Evaluating Impact on Safety of Improved Signal Visibility at Urban Signalized Intersections

A study evaluated the safety impacts associated with improved signal visibility at urban signalized intersections. The improvements included one or a combination of the following upgrades: signal lens size, new backboards, reflective tapes added to existing backboards, and additional signal heads. Intersection collision data based on insurance claim records from the Insurance Corporation of British Columbia were used in the study to evaluate the effectiveness of the signal visibility improvement. These automobile insurance claim data are current, comprehensive, and considered quite reliable for intersection locations. Traffic volume and collision data were collected for treatment and comparison groups. The treatment group included 139 intersections and the comparison group included 85 intersections. The data for the comparison group were used to account for history and maturation confounding factors. An empirical Bayes analysis was used to ensure that the evaluation results were reliable and to account for the regression-to-the-mean confounding factor. The analysis was undertaken for both severe (injury + fatal) and property-damage-only (PDO) collisions and also for daytime and nighttime collisions. The evaluation results indicate statistically significant reductions of 8.5%, 5.9%, 6.6%, and 7.3% for PDO, daytime, nighttime, and total collisions, respectively. Severe collisions showed a nonsignificant reduction of 2.6%.

[1]  B. Cole,et al.  Specification of Road Traffic Signal Light Intensity1 , 1968, Human factors.

[2]  Tarek Sayed,et al.  Traffic accident modeling: some statistical issues , 2006 .

[3]  Tarek Sayed,et al.  Evaluating the Insurance Corporation of British Columbia Road-Safety Improvement Program , 2004 .

[4]  Tarek Sayed,et al.  Accident Prediction Models for Urban Unsignalized Intersections in British Columbia , 1999 .

[5]  M Freedman.  TRAFFIC SIGNAL BRIGHTNESS REQUIREMENTS FOR THE NIGHTTIME DRIVING ENVIRONMENT , 1985 .

[6]  Kenneth Wade Ogden,et al.  Safer Roads: A Guide to Road Safety Engineering , 1995 .

[7]  Tarek Sayed,et al.  Safety Evaluation of Alternative Signal Head Design , 1998 .

[8]  Tarek Sayed,et al.  Using claims prediction model for road safety evaluation , 2001 .

[9]  F R Hulscher.  PHOTOMETRIC REQUIREMENTS FOR LONG-RANGE ROAD TRAFFIC LIGHT SIGNALS , 1975 .

[10]  Ezra Hauer,et al.  OBSERVATIONAL BEFORE-AFTER STUDIES IN ROAD SAFETY -- ESTIMATING THE EFFECT OF HIGHWAY AND TRAFFIC ENGINEERING MEASURES ON ROAD SAFETY , 1997 .

[11]  Gerhart F King.  VISIBILITY OF CIRCULAR TRAFFIC-SIGNAL INDICATIONS , 1981 .

[12]  W S Wainwright.  TRAFFIC SIGNALS, THE MANUAL ON UNIFORM TRAFFIC CONTROL DEVICES AND INTERSECTION SAFETY: DOING MORE THAN THE MINIMUM , 2004 .

[13]  Tarek Sayed,et al.  Evaluating Safety of Urban Arterial Roadways , 2001 .

[14]  R E Craven.  AN ANALYSIS OF TRAFFIC SIGNAL SAFETY IMPROVEMENTS , 1986 .

[15]  M. S. Janoff.  TRAFFIC SIGNAL VISIBILITY: A SYNTHESIS OF HUMAN FACTORS AND VISUAL SCIENCE LITERATURE WITH RECOMMENDATIONS FOR REQUIRED RESEARCH , 1994 .