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-- Expected Forecasts Gateway Constraints -- The TVTC recognizes that the gateways act as constraint points regulating flow into : and out of the area. Thus, the demand vol-mes will never actually be reached, Based on their inability to get through the gateways, motorists will adjust their schedules to travel outside the peak hour or to carpool or use trs_nsit. This adjustment in travel ; schedules, which could be reinforced with ramp metering, will be most obvious on the freeways and at interchanges. At intersections farther from the freeway, we can be _ less certain about adjustments to travel behavior. Motorists may adjust their sched- ules, or they may continue to travel during the peak hour but to a different destina- - tion, or other peak-hour trips may occur to replace the trips displaced by freeway congestion. Nevertheless, the plan is based on a Tri-Valley Model run in which the overcapacity gateway trips have been removed from the assigned traffic volumes. TMs is a major ass~_~mption. TVTO has agreed to treat the Alt~mont Pass, Vasco Road, Crow Canyon Road to Castro Valley, Dublin Grade, Sunol Grade, and 1-680 north as physical gateways. ' It is unrealistic to plan local transportation fadlities to accommodate all peak-hour traffic projected to flow through state highway gateways if this traffic in actuality cannot get through the gateways. Constrained as well as uncoustrained traffic volnmes ~--. have been developed for the Tri-Valley network. The constrained traffic vol-mes back down the assigned traffic volumes in proportion to the origins and destinations of the total gateway traffic. PM peak-hour, directional traffic volumes are shown in Fig- - ure 5-2 for 'unconstrained" traffic volumes, Figure 5-4 for the subtracted traffic, and on Figure 5-5 for the "gateway constrained" traffic volumes. The constrained vol-n~es are considered the baseline volumes. In order to develop rational action p]ana for local - arterials, beth unconstrained and constrained traffic volumes are shown in the plan. As actual capacities are more nearly reached monitoring of conditions may indicate the need to reassess and amend the current action plan. Level of service (LOS) at gateways for the constrained system is viewed to be no more than 1.0. Volume in excess of 1.0 which is projected is assumed to be spread over multiple hours of the peak period. The Plan espouses a policy of cooperation with adjacent jurisdictions to develop facilities management agreements in toms of ramp metering and freeway surveillance and control, which would fairly apportion available capacity in such a way that LOS F will be avoided except for unavoidable traffic incidents which create intermittent blockages of capacity. ~ Barton-Aschman Associates, Inc. 77