Why HOV lanes often don’t work

This post originally appeared in  Symposium Magazine.

In my article, I outlined a series of experiments that I and my team have run over the years that explain how people make decisions – some rational, some not – about their daily transportation habits. Today, I’m writing about one of the most popular traffic innovations in congested areas: High Occupancy Vehicle (HOV) and High Occupancy Toll (HOT) lanes.

HOV lanes are designed to expedite buses and cars that carry multiple passengers (and oddly, motorcycles). But there is often insufficient demand by drivers to fully utilize HOV lanes, while general-purpose lanes remain congested during the peak periods. This is inefficient.

If we simply opened up all lanes to all vehicles, we would lose the time saved for HOV vehicles and bus passengers. It would also make it difficult to restore HOV status to the lanes in the future — and people are more averse to losses than they are open to seeking gains. So the city of Minneapolis implemented a solution to transform the HOV lanes to HOT lanes on the I-394 corridor.

HOT lanes allow vehicles equipped with transponders to use what were the HOV lanes for a price. This toll varies with traffic conditions, but it aims to ensure that the HOT lanes maintain lower travel times than the general-purpose lanes. Travelers in a hurry might be willing to pay a premium to guarantee they can avoid congestion. Other travelers won’t.

Joined by Kathleen Harder and graduate students Shanjiang Zhu and Carlos Carrion (now a post-doc at the Singapore MIT Alliance for Research and Technology), I ran experiments to see how effective this switch really was. The aim was to use each commuter’s actual origin and destination but making sure they experienced alternative routes rather than staying bound to their usual route. We found out that there is a way to “price” an efficient commute – and I’ll write about that tomorrow.