Connecting cars electronically may benefit BRT as well

By Robbie Webber

As research on connected vehicle technology has advanced, writers have hailed the potential impact on traffic congestion and questioned the safety for non-motorized users of the roadways. But “talking cars” may also be a boon to bus rapid transit (BRT) as well.

For a BRT line to have maximum efficiency, it needs to operate in its own lane or a separate right-of-way. However, many communities are resistant to either giving up a general travel lane or widening the roadway to accommodate the BRT. But what if the lane were available to all users when there were no buses, and everyone had to move out of the way when buses came by? Then BRT vehicles could both have their own lane and not need a separate right-of-way.

That is the theory behind a “bus lane with intermittent priority” or BLIP. BLIPs are not a new idea, but the ability to have direct communication with vehicles and drivers, as opposed to requiring lighted lanes or signals at intersections, would theoretically make the system more efficient and, perhaps, cheaper. A new simulation by University of Arizona researchers Wei Wu and Larry Head shows how this would work. Signals from buses approaching from behind would alert drivers ahead of the bus that they need to move out of the bus priority lane, thereby allowing the bus a speedier passage. After the bus passed, drivers could move back into the lane.

However, for maximum efficiency, BLIPs rely on one of the most difficult variables in traffic modeling –driver behavior. As noted in a 2009 paper by the National Bus Rapid Transit Institute at the University of South Florida, their model assumed among other factors:

• the driving population was primarily commuter drivers familiar with the corridor;

• the driving population would be educated on how to use the BLIP system; and

• drivers would cooperate during BLIP operations to allow vehicles to exit the BLIP lane and enter the remaining traffic lane.

But where BRT is most useful, and where it also slows down, is where traffic is heaviest, so changing lanes is difficult, and drivers are tempted to use any opening to their own advantage. The magic element will be assuring that drivers respect the priority of the bus in the shared lane.

And that might be a problem. Emergency responders report that many motorists don’t pull over, even for police vehicles and ambulances.

Even the animation that accompanies the University of Arizona website does not really show much advantage for BRT. Not all drivers actually move out of the way, so the bus is still held up at the light by cars in front of it. In addition, the simulation does not show stops and the need to merge back into traffic –one of the most time-consuming maneuvers when buses share a lane with other vehicles.

Human behavior being what it is, connected vehicle technology probably isn’t as advanced as necessary for private vehicles to share a priority transit lane without compromising BRT operations and safety.

Robbie Webber is a Senior Associate at SSTI.