The existence of advance warning flashers (AWFs) challenges the necessity and effectivenessof advisory speed zones around high-speed intersections on rural and suburban highways. Nopublished guidelines or research currently exists for advisory speed limits in the vicinity ofhigh-speed intersections with advance warning flashers. The objective of this research was tostudy the operational effects of speed limit reductions in transitional speed zones on vehiclespeeds and speed variations. Seven AWF-equipped intersections in Nebraska with various speedlimit reductions were selected as test beds. Speed data was collected by Wavetronix sensor andwas classified and filtered to eliminate false calls and signal control effects. Quantile regressionmodels were used to conduct statistical assessments on the 15th, 50th, and 85th percentiles of thespeed distributions. At a 95 percent confidence level, the reduction from 65 to 55 mph led to a4.6 mph decrease in the 85th percentile speed and a 1.4 mph reduction in the inter-percentilerange between the 15th and 85th percentiles. The mean and standard deviation in speed wereestimated jointly by seemingly unrelated regression models. The 10 mph reduction from 65 mphresulted in a lowering of the mean speed of vehicles by 3.8 mph at a 95 percent confidence levelwithout impacting standard deviation significantly. The 5 mph reduction from 60 mph did notyield statistically significant results at the selected intersections.
展开▼
