An advanced curve warning system on an interstate route in northern California caused over 68 percent of drivers to reduce their speed.
The evaluation consisted of a comparison of speed data gathered before and after installation of the warning system, and surveys taken approximately 2 months and 10 months after installation. Speed data were collected using stopwatches to determine the speed of vehicles approaching the curves as the vehicles traveled over measured distances. Speed measurements were collected 9 months prior to the system’s installation and again 2 months, 5 months, and 10 months after operation began. Surveys of vehicle drivers were taken at a rest area within the corridor. One hundred and fifty-three (153) truck drivers completed surveys regarding the system 2 months after it began operation and 162 completed the second survey 8 months later. Eighty-nine (89) passenger car drivers completed surveys 2 months after operation began, and 77 completed the second survey. The report also discusses the crash statistics for the curves during the five years preceding installation of the warning system, but the short evaluation period following installation makes comparison of accident statistics invalid.
For three of the five curves, the reduction in the speed of trucks was statistically significant for at least one of the three data collection periods after the warning signs began operation. The two curves that demonstrated a significant reduction in truck speeds for all three visits after installation had downgrades greater than five percent. The speed reductions were smaller for the later visits to the curves, possibly indicating the drivers were becoming accustomed to the signs and paying less attention to them. Passenger vehicles also demonstrated significant speed reductions at two of the five curves. One curve recorded statistically significant speed reductions during the three site visits after installation of the warning system, while two of the post-implementation visits to another curve revealed significant speed reductions.
Author: Tribbett, Lani, et al.
Published By: California DOT
Prepared by the Western Transportation Institute and Montana State University for the California DOT New Technology and Research Program
Source Date: April 2000URL: http://www.coe.montana.edu/wti/wti/pdf/429861_Final.pdf
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