Development of Research Ideas:
(1) Opportunity for Crash Reduction from Offset Right Turn Lanes (OSRTLs) (for a total of $250,000): The objective of this project is to investigate what conditions present opportunities for crash reduction or prevention by the use of offset right-turn lanes at intersections of rural two-lane highways, and/or at intersections of rural multilane divided highways with rural two-lane highways. The proposed research will investigate what traffic, environmental, geometric, and safety performance conditions indicate potential for safety improvement from the use of OSRTLs.
(2) Safety Effects of Left Right Turn Lane Length at Signalized Intersection Along Five-Lane Arterials ($250,000): The objective of this project is to develop a design guideline on proper length of left-turn bay at intersection of 4-lane arterials with TWLTLs based on safety.
‘Evaluation of Flashing Yellow Arrows (FYA) For Protected / Permissive Left Turn (PPLT) Control’ was developed in August , 2010. The total budget of this proposal is $200,000 with the 25% match fund from SIUE. This research project seeks to quantify the safety and operational benefits from upgrading the left turn signal control for the permissive state from solid circular green to Flash Yellow Arrow (FYA) at signalized intersections. A thorough literature review will be performed to summarize the effectiveness of FYA on the intersection safety and operations based on previous researches by the Federal Highway Administration (FHWA) and other States’ Department of Transportation (DOT). National design manuals and other States’ policies on the use of FYA for Protected/Permissive Left Turn (PPLT) control will also be reviewed. The crash data, traffic volumes and geometric characteristics at all 72 signalized intersections in the Peoria area where the FYA signal is planned to be installed will be collected for an Empirical Bayesian (EB) before-and-after study. Safety Performance Functions (SPF) for PPLT with circular green signal control for the permissive left turn indication are to be established for the targeted crash types based on the crash data and general geometric data collected from the similar ‘control’ sites. SPFs will be used in the EB before-and-after study to take account for the potential ‘ ;regression-to-mean’ effects. Any differences in the traffic crash and injury frequencies and rates will be tested for statistical significance. An Excel evaluation tool will be developed for evaluating safety benefits of FYA when sufficient crash data has been accumulated for the ‘after’ period in the future. As it may take longer than the project period for a sufficient amount of traffic crash data for the ‘after’ ; period to accumulate, the traffic conflict studies involving left turn maneuvers will be conducted at the selected representative intersections (at least 35 locations) in the Peoria area. Camcorders and JAMAR traffic data collectors will be used to collect traffic conflicts, traffic volumes, gap acceptance data, and delays for left turn maneuvers for at least seven hours per location during the ‘before’ and the ‘after’ periods. Differences in the number of traffic conflicts, conflict rates, gap acceptance, capacity, and delays of left turn maneuvers will be tested statistically to determine the operational effectiveness of the upgraded signal control. The final findings of the safety and operational effectiveness of the FYA left turn signal control will be compiled into a final report. The recommendations will be provided to help IDOT establish a statewide policy on the use of FYA for PPLT control.