Wilbur Smith Associates DTR Traffic & Revenue Study re Toll Sensitivity, July 21, 2009

The following is an extract from the 2009 Wilbur Smith Associates study for MWAA, "Comprehensive Traffic and Revenue Study," on the impact of toll changes on Dulles Toll Road revenues and traffic.  This two-page section (pp. 5-8 & 5-9) discuss the sensitivity of of traffic to DTR toll increases.   We have added emphasis to the key sentence in this excerpt. 

The key point from this is analysis is that Wilbur Smith Associates believes that MWAA can raise tolls to $12 and beyond by 2023 and still increase toll road revenues.  This will come at some loss of ridership, but the rate increase will more than offset the loss of traffic on the toll road in their view. 
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TOLL SENSITIVITY

Toll sensitivity analysis tests a series of toll rates to aid in the selection of toll rate for the
DTR corridor. Future year toll sensitivity curves are based on changes in traffic
characteristics in the corridor including increasing congestion, value of time, competing
facilities, and inflationary trends. These curves are essential in estimating the viability of
future toll rate increases.

In general, the toll sensitivity curve suggests that when toll rates increase, a portion of
travelers will leave the toll facility in favor of other routes. Therefore, as the toll rate
increases transactions would tend to decrease. However, as the toll rates increase, toll
revenues increases until a point where a maximum revenue is generated after which
additional toll rate increases would generate a decrease in toll revenues.
Toll sensitivity analyses were conducted for the years 2010 and 2023. Figure 5-6
illustrates the daily toll sensitivity curves for these years estimated for the DTR. Main
line toll rates, in nominal year dollars, ranging from $1.00 to $12.00 were analyzed for
both 2010 and 2023.

The sensitivity analyses results indicate that the projected toll rates of DTR are well
below the estimated theoretical revenue maximization point. This demonstrates that there
would be considerable potential for revenue enhancement through toll increases above
current rates and even for those assumed for forecasting purposes, if needed.
Revenue-maximizing main line tolls are estimated to be somewhere above $7.00 in 2010
and somewhere above $12.00 in 2023. For ease of reference, each curve has been labeled
at projected toll rates in each year.