Case Study:

Sacramento, California

Application

Highway Scenarios

The study also compared the effects of high-occupancy roadway, land use, and pricing scenarios using the SACMET96 model. Except for the HOV-only scenario, these scenarios were not analyzed using the MEPLAN model. Nevertheless, the results are of interest because they illustrate the potentially synergistic effects of roadway, land use, and pricing scenarios, and they highlight the similarities and differences between HOV and HOT lane impacts.

Travel Impacts

The effects of the road-oriented policy scenarios in the Sacramento region are most strongly evident in the daily mode share projections for home-based work trips because these are the trips largely targeted by the HOT and HOV policies. It is in this trip purpose that congestion is most severe. For both the 2005 and 2015 scenarios, the HOV and HOT scenarios alone have a small impact on mode share. For the 2015 scenarios, the addition of the RODs to the HOT and HOV policies makes the mode share impact more noticeable. Drive-alone share decreases by about 1.5 percent, most of which is shifted to shared-ride. The addition of the pricing policies to the ROD scenarios further intensifies the effect, with a decrease in drive-alone mode share of up to four percent. The mode share trends for total regional trips are similar to those described above, but differences among scenarios are smaller because they include all trip purposes.

Daily vehicle travel projections for the 2015 scenario are presented in Figure 13. For both the 2005 and 2015 scenarios, the HOV and HOT scenarios result in small increases in vehicle trips VMT and greater reductions in VHD (5.2 to 7.7 percent). In the 2015 scenarios, the addition of RODs to the HOV and HOT scenarios produces an increase in vehicle trips, because of greater auto accessibility in the RODs, but reduces VMT. Thus, it appears that the ROD scenarios result in more but shorter vehicle trips. The addition of the RODs to the HOV and HOT scenarios significantly increases the reduction in VHD.

Figure 13.
Roadway and Land Use Scenarios: SACMET96 Model
Travel, Percent Change from Base Case (2015)

Source: Johnston, Rodier, Choy, and Abraham (2000).

The addition of the pricing policies to the HOV & ROD and HOT & ROD scenarios tends to dampen the increase in vehicle trips, increase the reduction in VMT, and increase the reduction of VHD, with a delay reduction of 23 percent in the HOT, ROD & Pricing scenario. In each case, the HOT option provides larger reductions in VHD than the HOV option. The HOT policies provide faster auto travel times, and thus lower VHD, than the HOV lanes because the tolls result in more efficient use of the new lanes.

Previously, it was found that the 2015 Light Rail scenario reduces vehicle trips by 0.1 percent, VMT by 0.3 percent, and VHD by 2.4 percent. Thus, with respect to reduction in VMT, the Light Rail scenario is superior to both the HOV and HOT scenarios, which increase VMT. However, with respect to reductions in delay the HOT scenario is best, followed by the HOV scenario, and then the Light Rail scenario. Considering land use and pricing policies, the same conclusions hold, although with significantly higher magnitudes of impacts in each case. The transit scenarios are preferable for reducing VMT, but the highway scenarios are preferable for reducing roadway delay.

Emissions Impacts

Impacts on daily vehicle emissions tend to correspond to VMT increases. Thus, both the HOV and HOT scenarios result in increased emissions over the base case scenario, and the HOT scenario produces slightly greater increases in emissions than the HOV scenario (Figure 14). Increased roadway capacity tends to speed up auto travel times, and thus auto travel distances (VMT) and emissions increase.

Figure 14.
Roadway and Land Use Scenarios: SACMET96 Model
Travel, Percent Change from Base Case (2015)

Source: Johnston, Rodier, Choy, and Abraham (2000).

The addition of the RODs to the HOV and HOT policies reverse the increase in emissions. However, the reduction in emissions is relatively small (approximately 2.0 percent for VMT and TOG, and slightly less for NOx). It was found earlier that TODs with similar regionwide shifts in new development and light rail and feeder bus service along similar corridors would produce a 6.5 percent reduction in VMT and a 5.6 reduction in TOG at the regional level. These results suggest that land use intensification policies may be more effective in reducing VMT and emissions when they are combined with transit than with HOV or HOT lane policies.

The addition of pricing policies to the HOV and HOT scenarios increases the reduction of emissions, although again, the reduction is smaller than for pricing in combination with transit and land use policies.

User Benefits

The change in economic benefits from the base case scenario (1995 present value) is shown in Figure 15. The HOT scenario produces larger economic benefits than does the HOV scenario ($0.01 versus $0.09 per trip for 2015). The HOV scenario results in a small economic loss when the full, unobserved cost of additional travel is included in the analysis. The HOT scenario results in an economic benefit because of the travel time saving to travelers with high values of time, which more than offsets the unobserved cost of additional travel.

Figure 15.
Roadway and Land Use Scenarios: SACMET96 Model
Economic Benefits Per Trip vs. Base Case (2015)

Source: Johnston, Rodier, Choy, and Abraham (2000).

In 2015, the addition of the RODs and then the pricing policies to the HOV and HOT scenarios both increase the economic benefits of the scenarios. This is because of the travel time saving that results from the RODs and the pricing policies. It is also assumed that revenues from the pricing policies are returned to the public (e.g., through lower sales taxes). Overall, the scenarios that combine RODs and pricing policies with HOT lanes have nearly double the benefits of the same policies combined with HOV lanes. The economic benefits for the HOT & ROD and the HOT, ROD & Pricing scenarios ($0.08 and $0.15, respectively) are comparable to those obtained from the Transit & TOD and the Transit, TOD & Pricing scenarios ($0.10 and $0.15).

Conclusions

HOV lanes and, to a lesser extent, HOT lanes are considered politically feasible policies in the Sacramento region to address the problems of congestion and emissions associated with regional transportation systems. The results of this study indicate that HOT lane policies may be somewhat better than HOV lane policies at reducing congestion. However, both the HOV and HOT scenarios increase VMT and emissions compared to a no-build scenario and the increase in emissions is greater for the HOT scenario compared to the HOV scenario. The Light Rail scenario is more effective at reducing VMT and emissions, but less effective at reducing congestion, than the HOV and HOT scenarios.

Combining land use intensification policies (RODs) and pricing policies with the HOT and HOV scenarios may produce added benefits with respect to congestion and emissions. The RODs and pricing policies are both found to reduce congestion, although more so in the HOT scenarios than in the HOV scenarios. The RODs and pricing policies are also found to decrease VMT and emissions; the benefits for these measures are small, however, especially when compared to TOD scenarios. These results suggest that land use intensification policies may be more effective at reducing VMT and emissions when they are combined with transit rather than with HOV and HOT lanes.

The results of this analysis indicate that HOV and HOT scenarios are not significantly different with respect to VMT, vehicle delay, and emissions; the HOT scenario, however, is clearly superior to the HOV and Light Rail scenarios as measured by user economic benefits. Economic losses for the HOV lanes are offset, and gains for the HOT lanes are increased, when the policies are combined with RODs and pricing policies. These increases in economic benefits are obtained from greater accessibility to carpooling and express transit service in the RODs and reduced congestion resulting from the pricing policies. The most beneficial roadway and land use scenarios provide similar economic benefits as the most beneficial transit and land use scenarios. In each case, these benefits are increased further when combined with pricing.

[TOP]