Trip Generation

Trip Generation validation was considered for both production ratios and relative shares.

Ratios

Validation for production ratios looked at three sets of measures: productions-to-household ratios (Figure 1), total trips (Figure 2), and trip balance ratios (Figure 3). The sources of the data include the Utah Household Travel Survey from 2012 (2012 HTS), the base year model (BY 2019 Model), and the National Household Travel Survey from 2017 with data from the Mountain Census Division (2017 NHTS - Mountain).

The model shows an average 4.01 trips per person which is slightly higher than the 2017 NHTS - Mountain average of 3.54. The model also shows an average 12.4 trips per household which is higher than the 2017 NHTS - Mountain average of 9.1. Utah, including the Wasatch Front, has a significantly higher average household size of 3.09 persons per household when compared to the Mountain Census Division average of 2.58, which accounts for the differences when compared to the 2017 NHTS - Mountain averages.

Figure 1: Productions to Households Ratios – Total Trip Ends (II + IX).
Figure 2: Total Trip Validation
Figure 3: Trip Balance Ratios

Relative Shares

Validation for production relative shares considered the reasonableness of relative shares as shown in Table 1. The relative share between HBW, HBO and NHB trips looks reasonable with HBW at about 14% of the total and the highest share going to HBO. Commercial vehicles account for about 22% of the total trips generated by the model. This is within the expected range for an urban area like the Wasatch Front. IX and XI trips account for around 2% of the total trip generation. This also appears to be reasonable.

Table 1: Relative Shares of Trip Productions
Purpose Production Share
HBW 1,758,104 14.1%
HBO 5,317,476 42.5%
     HBShp 908,733 7.3%
     HBOth 3,719,191 29.7%
     HBScK6 365,084 2.9%
     HBsc712 324,468 2.6%
NHB 2,405,720 19.2%
     NHBW 812,855 6.5%
     NHBNW 1,592,865 12.7%
Total Person 9,481,300 75.8%
Total External 172,855 1.4%
     IX 78,057 0.6%
     XI 94,798 0.8%
Total Truck 2,802,234 22.4%
     LT 1,553,653 12.4%
     MD 884,558 7.1%
     HV 364,023 2.9%
Total IX Truck 21,750 0.2%
     IX MD 10,716 0.1%
     IX HV 11,034 0.1%
Total XI Truck 30,741 0.2%
     XI MD 14,372 0.1%
     XI HV 16,369 0.1%
Telecommute Share of HBW 69,175 0.6%
Telecommute Share of NHBW 19,552 0.2%
TOTAL 12,508,880 100.0%