Investigation of the Impact the I-94 ATM System has on the Safety of the I-94 Commons High-Crash Area

Project summary:

Active traffic management (ATM) strategies are being deployed in major cities worldwide to deal with pervasive system congestion and safety concerns. While such strategies include a diverse array of components in the Twin Cities metropolitan area, the deployment of intelligent lane control signs (ILCS) allowed for the implementation of variable speed limits (VSL). The VSL system in the Twin Cities aims to detect congestion and preemptively warn upstream drivers to reduce speed. By reducing the severe change in speed between upstream and downstream traffic, safety and operational benefits are sought. This project investigated the effect the I-94 VSL system has on the safety of the high frequency crash area located on the westbound lanes of the freeway through downtown Minneapolis (I-94/I-35W commons).

This research used several methodologies to examine the impact of the VSL system within the I-94/I-35W commons high-crash area. Numerous data sources were used, including video records of crash and near-crash events, loop detector traffic measurements, machine vision sensor data, and actuations from the VSL system. A before-and-after approach was taken to examine the incident rates for crashes and near crashes using visually identified events within video data.

Utilizing the unique capabilities of the Minnesota Traffic Observatory's I-94 Freeway Lab, high-resolution traffic measurements, collected by machine vision sensors at the bottleneck location, were used within a new cross-correlation-based analysis methodology to measure and visualize shockwave activity before and after the implementation of the VSL system.

• OST-R summary report for this project (PDF)