UofT researchers report on optimized tolling for GTA freeways

Dr. Aya Aboudina and her thesis advisor, Prof. Baher Abdulhai, recently completed a six-year long study on congestion pricing and dynamic tolling on freeways in the GTA.

The study methodology optimizes the timing, location and magnitude of tolls on freeways in the GTA to reduce system-wide congestion, most notably on freeways but without overloading adjacent arterials.  “The dynamic tolls spread traffic more evenly over time (the peak period) and space (freeways and arterials) such that the net effect is positive. What you want to avoid is over-shifting traffic to arterials inducing net loss for motorists”, Abdulhai says.

The study found that time-varying tolls, which incentivize some (not all) motorists to alter when they travel, reduce the number of drivers rerouting to adjacent surface streets.  On the other hand, they found that flat-rate tolls, which do not vary with time, do not induce temporal shift, and may in fact induce excessive routing off freeways. “Diverted traffic can overload the parallel arterials and back up onto the freeway itself, preventing toll payers from further travelling along the tolled freeway, which is counterproductive”, Aboudina explained.

The study examined the optimal tolls for the Gardiner, DVP and the 401 in the GTA during the morning peak.  For example, the results of their study recommend that tolling the Gardiner Eastbound in the morning, should start at 7:00  AM, gradually increase from zero to 16 cents per km at 8:00 AM and gradually drop to zero cost at 9:30 AM.  This pattern mirrors the pattern of congestion during the peak, being highest when congestion is worst.

“Our perspective is that tolling is a viable traffic and congestion management tool, much as traffic lights are.  Tolling revenues are a by-product”, Abdulhai says.

Aboudina further shows that the benefits of the proposed tolling structure exceed the costs for both the government and the toll payers. The benefits are materialized even before the toll revenues are spent (possibly on enhancing transit and road infrastructure).

The research, which was the subject of Dr. Aboudina’s recently completed dissertation, will be presented at ITS Research Day on December 2 at the University of Toronto. You can register for the event here.