🧹 Chore: Account for Minimum Toll on Express Lanes

[DavidOry]

At least the MTC-operated Express Lanes have a minimum toll value of 50 cents. When setting the distance-based toll rates in the model, there is currently no good way to ensure users pay a minimum of 50 cents.

Progress:

• Sufficiently defined
• Approach decided
• Implemented

Considerations

There are several, as follows:

• Emme has an alternate roadway assignment procedure called ptoll that is built for this type of use case. This would allow the roadway pathbuilder to build the correct paths with the minimum toll in place.
• @FlaviaTsang is looking into whether the Express Lanes operated by VTA and ACTC have similar policies
• An easy fix in the near term is to modify the mode choice UEC so that the toll modes are see a minimum cost of 50 cents.

cc @gregerhardt, @lmz

[DavidOry]

Could also do this in the skim, by setting a minimum toll price of 50 cents. Ancillary benefit is reducing very short trips on the express lanes, which is observed.