ALDOT Pilot Study of Evaluating A Mobile-based Curve Safety

Horizontal curves account for approximately a quarter of fatal crashes. Because existing programs to improve the safety of horizontal curves are costly in terms of both time and resources, the Alabama Department of Transportation (ALDOT) is exploring a new Mobile-based Curve Safety Evaluation Tool (MCSET) (developed in the NCHRP IDEA Project 214 (1) and GDOT project (RP 20-22 (2)) as a cost-effective alternative method to assist the curve safety evaluation. The purpose of this pilot study is to critically assess the practicality of the MCSET method for performing curve safety evaluations on ALDOT’s roads and provide recommendations on its potential applications, including determining adequate advisory speed and MUTCD-compliance curve sign design.

Controlled Site Tests on Test Track at NCAT

Road Tests on Selected Curves on ALDOT Roads

Outcomes

Task 1: Design of Controlled Site Tests and Road Tests (AU and SRS)

Designed controlled site tests and road tests in terms of where and what data was collected
Worked collaboratively with ALDOT on setting criteria and selecting routes for road tests

Task 2: Data Collection and Field Test (AU and SRS)

Collected data in a consistent manner based on the design in Task 1
Adjusted data and speed based on the traffic condition at site
Collected multiple runs of data on selected curves first based on Road Test Design following guidelines for each method
Collected three passes of data for each designed outcome
Gathered existing curve signs on selected road section to serve as a reference in later analysis
Provided the GIS shape files for the selected routes and NCAT test track by ALDOT

Task 3: Process and Analyze Data (AU and SRS)

Processed data collected by the Rieker CARS unit and the MCSET smartphone units using the methods developed in the NCHRP IDEA Project 214 and GDOT RP 20-22
Reported data on curve geometric information (e.g., radius, point of curve (PC), and point of tangent (PT)), 95th percentile superelevation along a curve categorized by ranges of (e.g., flat, moderate, steep, and very steep), advisory speed, and curve warning sign planning including sign location and MUTCD code
Analyzed processed data to evaluate the comparability and repeatability of the MCSET method

Task 4: Summarize and report findings (AU)

Summarized findings
Provided recommendations on the use of the MCSET method for performing curve safety evaluations