Maverick Engineering Social Media

Chulsu Yang – Movin’ Down the Highway

Anyone who has driven on the LBJ Freeway in north Dallas has encountered an increased heart beat rate while trying to enter the freeway. Imagine what it’s like for a driver trying to cross three-or-four lanes of fast moving traffic to try to get to the high-occupancy vehicle (HOV) lane. Very fast moving, in most cases, and drivers can only gain access to and exit the HOV lane at designated sections of the freeway.

HOV lanes are a good way to increase the capacity and improve the operations of urban freeways. They encourage carpooling and ridesharing, which in turn reduces congestion by putting fewer vehicles in the general purpose lanes. But how much distance does a driver need to safely weave across the lanes from the entrance ramp to reach the HOV lane?

Civil engineering doctoral student Chulsu Yang knows. He’s been studying the problem for two years and he and his team are currently writing up a report for the Texas Department of Transportation (TxDOT).

Yang and his supervising professors, Drs. Jim Williams and Steve Mattingly, received a two-year, $213,000 grant to develop guidelines for TxDOT to use in marking the entrances to and exits from HOV lanes. The team, which included other graduate students, involved field studies to observe first-hand actual traffic conditions at different sites, at various times of the day and in different directions. They also captured traffic video using their own camera and the pole-mounted TxDOT surveillance cameras.

How bad is the traffic on LBJ? According to a 2004 study, more than 120,000 cars a day travel the stretch between Montfort and Preston Road, near the Galleria. This is far in excess of the designed traffic volume.

The shift to HOV and managed lanes is increasing in cities across Texas, so it’s essential that TxDOT has the best information possible for establishing design standards. The existing guidelines for HOV lanes, it turns out, don’t account for real-world environments and driver behavior. Yang’s study, for instance, discovered that current distances from LBJ entrance ramps to HOV lanes vary from 1,290 feet to 6,060 feet, all involving four lanes of traffic.

Yang and his team took the data they gathered in the field, developed computer simulations to evaluate different traffic and distance scenarios, and created a new set of guidelines for TxDOT’s road design manual.

So, sometime soon, expect to see some changes in entrance and exit markings for HOV and managed lanes on the freeway. They’re there to safely speed you on your way, thanks to research performed by Chulsu Yang.