Add Safety Metrics Module to standard VERSPM

[jrawbits]

The new CalculateSafetyMeasures module in VETravelPerformance works in VERSPM_MM but fails in regular VERSPM (even after the required safety rates input, marea_safety_factors.csv, is present) due to missing BikeAvgTripDist (which is not computed in the standard VEHouseholdTravel).

Workaround for now is to use VERSPM_MM in the standard distribution if you're interested in the safety rate computations.

Here's how we could fix VEHouseholdTravel, per Brian Gregor:

"There is information in the model to compute an estimate of bike miles of travel from bike trips when the MM travel model is not used. The DivertSovTravel module computes the average trip length of diverted SOV trips. This is used for the purpose of calculating diverted trips from diverted miles to add to the diverted trips to the bike trips computed by the CalculateAltModeTrips module. The average trip length for diverted SOV trips is saved as the 'AveTrpLenDiverted' dataset in the 'Household' table. Although this could be used to convert bike trips into miles, I think it would be better to estimate [from other sources] an average bike trip length and average walk trip length and have these be inputs to the CalculateAltModeTrips modules. That module code would also be modified to calculate bike trip miles and walk trip miles. Those quantities would be saved to the datastore using the same names as used in the MM travel model. That way the safety module could run without any alterations."

[jrawbits]

In the new VE 3.0 module and model structure, I'm inclined in the short run to move the CalculateSafetyMeasures module into the VETravelDemandMM package and add it to the MM variant of VERSPM, so it's not readily available for standard VERSPM.

Implementing the proper fix proposed by Brian Gregor for VEHouseholdTravel (to provide bike and walk mile averages as inputs and use them to generate the missing fields for BikeAvgTripDistance) is probably the way to go to get the safety rates available in standard VERSPM.