Saturday, December 1, 2012

CMAP Congestion Pricing Plan

Chicago Metropolitan Agency for Planning (CMAP) is planning to implement congestion pricing in the Chicago region as part of the GO TO 2040 plan. The current congestion pricing plan of CMAP only focuses on express toll lanes. The selected freeway segments for dynamic tolling include new lanes on the I-90 Addams Tollway, the I-290 Eisenhower Expressway, and the I-55 Stevenson Expressway plus two new facilities, the Illinois Route 53 north extension and Illinois Route 120 bypass and the Elgin-O'Hare West Bypass.

To support the plan, CMAP has released a report quantifying "some of the benefits of congestion pricing, such as travel time savings, and also examining potential drawbacks, such as impacts on local streets and inequity among users." The report has reasonably studied the benefits and drawbacks of the plan. However, I think it has room for improvement. To determine more effective pricing plans, a more comprehensive study is required. Specifically, existing time-dependent travel times on the selected corridors need to be compared with the modeled travel times before and after pricing. Currently, the CMAP report only uses daily VMT for validation purposes. A future step to improve the analysis would be a time-series analysis of traffic flow and speed considering the "temporal spreading" effect when roads are dynamically priced. Temporal spreading refers to the change in travelers' departure time to avoid high congestion prices in the peak periods. Also, the reported changes in travel times on arterials and freeways seem (to me) to be over estimated. Note that no discussion on "induced demand" is provided.

Moreover, congestion pricing should not only be limited to express toll lanes. Cordon pricing, such as those that have been implemented in London or Singapore, should be considered as well. Downtown Chicago, an area roughly bounded by the Division St on North, Halsted St on West, Roosevelt St on South, and Lakeshore Drive on East, is a highly congested area during morning and afternoon peak periods which can potentially be priced. An alternative plan to mitigate congestion in downtown Chicago is metering the input rate into downtown based on the prevailing congestion level. A similar plan has been implemented in Zurich, Switzerland.

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