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42 CHAPTER 12 CASE STUDY 3B: REMOVE FREEWAY HOV LANE Case Study 3b removes the freeway HOV lanes (one HOV case trip tables by time period (AM peak, PM peak, and off lane in each direction) from a freeway in an urban area. The peak) and by mode (SOV, HOV, and transit). The revised trip freeway is uncongested before removal and becomes con- tables were then reassigned to the improved network to deter- USER'S GUIDE gested after the removal of the lanes. mine the impact on VMT, VHT, and emissions. The results The specific location for this case study is a 2-mile-long are summarized in Tables 30 through 32. section of the Interstate 5 freeway feeding downtown Seat- This case study illustrates the impacts of closing an HOV tle, Washington (see Figure 9). facility on a freeway that is near capacity. The effect is to increase congestion on the freeway in the mixed-flow lanes in the peak direction of travel (reverse commute is generally 12.1 APPLICATION unaffected). The I-5 freeway mainline has four lanes in each direction The travel time in the peak direction is increased from 6 to with a 45-mph free-flow speed and 1,800-vph/lane capacity 50 percent during the peak periods. Peak-period traffic (HOV and an HOV lane in each direction with a 60-mph free-flow plus SOV) on the facility is reduced by almost 10 percent. speed and a 1,500-vph/lane capacity. In this project, the HOV The result of the HOV lane closure is a 0.02-percent reduc- lanes in both directions are removed. Thus, the section now tion in regional daily VMT and a 0.06-percent reduction in has four lanes in each direction and no HOV lane. mobile source emissions. 12.2 CASE STUDY RESULTS The NCHRP 25-21 methodology was used to compute the impacts of the traffic-flow improvement on the 2020 base

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43 Project USER'S GUIDE Figure 9. Case Study 3b: Remove HOV lanes from I-5. TABLE 30 Case Study 3b: Travel time changes on the facility Period Scenario NB SB V/C Speed (mph) Time (min) V/C Speed (mph) Time (min) AM Peak Before 0.90 35.7 3.84 0.57 36.6 3.70 After 0.94 35.0 4.06 0.67 36.6 3.70 Difference 0.04 -0.7 0.22 0.10 0.0 0.00 % Difference 4.66% -1.84% 5.73% 18.01% 0.00% 0.00% PM Peak Before 0.71 37.1 3.61 0.91 36.6 3.70 After 0.82 37.1 3.61 0.96 31.4 5.44 Difference 0.11 0.0 0.00 0.05 -5.2 1.74 % Difference 15.69% 0.00% 0.00% 5.32% -14.21% 47.03% Off Peak Before 0.39 37.1 3.61 0.36 36.6 3.70 After 0.46 37.1 3.61 0.42 36.6 3.70 Difference 0.07 0.0 0.00 0.06 0.0 0.00 % Difference 19.30% 0.00% 0.00% 17.71% 0.00% 0.00% TABLE 31 Case Study 3b: Volume changes on the facility Period Direction Before After Difference %Difference AM Peak NB 22,667 19,439 -3,229 -14.24% SB 14,256 13,809 -447 -3.14% TOT 36,923 33,248 -3,676 -9.96% PM Peak NB 17,771 16,865 -906 -5.10% SB 22,799 19,706 -3,093 -13.57% TOT 40,570 36,571 -3,999 -9.86% Off Peak NB 57,936 56,577 -1,359 -2.35% SB 54,086 52,309 -1,777 -3.29% TOT 112,022 108,886 -3,136 -2.80% Total NB 98,374 92,881 -5,493 -5.58% SB 91,141 85,824 -5,317 -5.83% TOT 189,515 178,705 -10,810 -5.70%

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44 TABLE 32 Case Study 3b: Regional results Scenario Period VMT VHT Speed THC CO NOX (mi) (hrs) (mph) (gm) (gm) (gm) Before AM Peak 12,152,900 381,540 31.9 PM Peak 15,261,700 518,222 29.5 Off Peak 37,208,800 1,179,200 31.6 Total 64,623,400 2,078,962 31.1 45,000,186 714,064,881 46,356,879 After AM Period 12,151,000 381,565 31.8 PM Period 15,254,600 517,364 29.5 Off-Peak 37,205,400 1,179,400 31.5 Total 64,611,000 2,078,329 31.1 44,973,564 713,524,692 46,320,617 Difference -12,400 -633 0.0 -26,622 -540,189 -36,262 % Difference -0.02% -0.03% 0.01% -0.06% -0.08% -0.08% USER'S GUIDE