TRIP DISTRIBUTION

a$.$ A production$-$constrained version of the gravity model has been calibrated using the data

collected in $2020.$ The results of this calibration effort reveal that the following friction

factor function ensures that the gravity model fits the observed base year trip "length"

frequency distributions reasonably well:

$f(c_{iy})=c_{ij}^{-b}$

where

$c_{ff}=$ travel time $($in minutes$),$ i to j

$b=1\mathrm{.}5,$ for work trips

$b=2\mathrm{.}0,$ for non$-$work trips

b$.$ Work trips and non$-$work trips should be distributed using the following work indices and

non$-$work indices, respectively, as measures of the "attractiveness" of each zone in the

year $2030.$

c$.$ Distribute the total $($AM plus PM$)$ peak work person trip productions and total $($AM plus

PM$)$ peak non$-$work person trip productions to obtain the total $($AM plus PM$)$ peak

person trip production$-$attraction interchanges for each of the two purposes for the year

In doing so$,$ assume that the travel times in the existing transportation system

$($Figure $2)$ will be maintained in the future $($note that the zone$-$to$-$zone travel time includes

the travel time on the arterial and$/$or the freeway plus the travel time from the network

node to the zone centroid; the intra$-$zonal travel times may be assumed to be the same as

the time from the zone$-$centroid to the network node$).$

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