Travel Demand Model - OKI

OKI/MVRPC Travel Demand Model – Version 6.03.3 Truck Percentages of Assigned VolumeTruck percentages of total assigned daily volumes for the base-year model are shown in Table 3.6,grouped by link functional classes. System-wide, trucks constitute 7.4 percent of traffic in motion,ranging from a high of 14.2 percent of interstates freeway flows to a low of 4.2 percent on local roads.On major and minor arterials and major collectors, trucks comprise less than 5 percent of traffic volume.On ramps, expressways and minor collectors, trucks represent between 6 and 7 percent of assignedvolume. These truck percentages are typical of the respective roadway classes.Table 3.6. Truck Percentage of Daily Assigned Traffic by Link ClassDaily VolumesNumber ofFunctional Class Total Trucks Total Vehicles Observations Percent Trucks1. Interstates 5,970,097 42,152,545 1,149 14.2%2. Major Arterials 1,783,371 39,031,977 3,994 4.6%3. Minor Arterials 1,576,040 31,859,952 5,084 4.9%4. Major Collectors 1,040,130 23,480,029 8,237 4.4%5. Minor Collectors 57,205 822,542 962 7.0%6. Local Roads 146,266 3,480,645 3,001 4.2%8. Ramps 599,131 8,938,937 1,422 6.7%9. Expressways 254,102 4,162,588 275 6.1%Total Observations 11,426,342 153,929,215 24,124 7.4%3.4 Truck Trip-Length ProfilesThe distribution of SU and MU truck trip lengths for the peak period assignment of the base-year CRM areshown in Figures 3-1 and 3-2, below. The graphs show patterns very similar to those used to create theseed matrix, with the distribution of SU truck trips peaking around the 10-minute mark and a mean triplength of 20.3 minutes for internal-internal trips. The distribution of MU internal-internal trips peaksaround the 15-minute mark with a mean trip length of 35.7 minutes. Intra-zonal (TAZ) trips were notincluded.For comparison, trip distribution profiles are shown that include all internal and external trips. Absoluterather than proportional trip frequencies were use to show the increment in the number of trips thatexternal stations contribute to total SU and MU trips. The “spikes” on the graphs are produced by trafficcrossing the study area between external stations. For example, the very large spike around the 31-minute mark of the MU trips graph most likely includes a large component of EE flows along I-70 throughnorthern Montgomery County. Including EE and EI trips in the calculation of mean trip lengths onlyprovides a lower bound on the average amount of time that truck trips spend on the network. Since oneor both ends of EE/EI trips are not observed, actual trip lengths are censored.Figures 3-3 and 3-4, below, show the trip-length profiles for SU and MU truck trips during the off-peakassignment periods. The shapes of the distribution curves are similar to those of the peak period;however, mean trip lengths are noticeably shorter. The mean trip lengths for internal-internal off-peaktrips are 16 minutes for SU trucks and 27.6 minute for MU trucks.Truck Model - Base-Year Truck Model Results 39