Knowledge Resources

A microscopic simulation approach was used to evaluate the effects of an Automated Workzone Information System (AWIS) deployed near Los Angeles, California on Interstate 5 between Magic Mountain Parkway and Rye Canyon Road. The AWIS included vehicle detectors and three portable Dynamic Message Signs (DMS). During construction, the AWIS was deployed to manage traffic on the interstate, which has four lanes in each directions separated by a median. One southbound lane and one northbound lane adjacent the median were closed. A parallel arterial route with one lane in each direction, the Old Road, was recommended to motorists as an alternative when the freeway was congested. Based upon detected traffic conditions, the following messages were displayed on the DMS:

• TRAFFIC JAMMED alternating with SOUTH 5 AT RYE CANYON.
• SLOW TRAFFIC AHEAD alternating with PREPARE TO STOP.
• TRAFFIC JAMMED NEXT 2 MI alternating with EXPECT 5 MIN DELAY.
• TRAFFIC JAMMED AHEAD alternating with 126 FWY TO MAGIC MOUNTAIN.
• SOUTH 5 TRAFFIC JAMMED alternating with AUTOS USE NEXT EXIT.
• JAMMED TO MAGIC MOUNTAIN alternating with EXPECT 10 MIN DELAY.
• JAMMED TO MAGIC MOUNTAIN alternating with EXPECT 15 MIN DELAY.

The evaluation focused only on southbound Interstate 5 due to severe congestion levels. The simulation network was designed in PARAMICS (PARAllel MICroscopic Simulation) using aerial photos, road geometry, and infrastructure maps. Other basic input data included vehicle mix by type, vehicle characteristics, traffic control and vehicle detection system data, traffic analysis zone information, and driver behavior data. The simulation network had one major bottleneck, caused by the work zone lane closure at Rye Canyon Road.

Data for the "before" study were collected on May 18, 2003 when the work zone was in place and the AWIS was not deployed. Data for the "after" study were collected on September 1, 2003 (during the Labor Day Holiday weekend) following AWIS activation. Traffic volume data were collected using pneumatic tube vehicle detectors, loop detector data from the California Freeway Performance Measurement System, and by manual counts. Travel time data were collected with GPS-equipped probe vehicles.

Field data were used to calibrate two simulation models to traffic conditions before and after AWIS deployment. A two-stage heuristic solution algorithm was used to simultaneously estimate the origin-destination demand matrices and routing parameters. Performance metrics were calculated by comparing the simulation results of two scenarios:

• Without AWIS – the "after" demand pattern with routing parameters in the "before" model.
• With AWIS – the "after" demand pattern with routing parameters in the "after" model.

FINDINGS

After the AWIS was deployed, the diversion rate increased by 4.3 percent (which was equivalent to an additional 224 vehicles per hour on the arterial route). This diversion reduced Vehicle Hours Traveled (VHT) by nearly 37 percent and increased Vehicle Miles Traveled (VMT) by almost 15 percent. As a result, average network speed increased by 81 percent.