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Expected Forecasts Gatewoy Constraints The TVTC recognizes that the gateways act as constraint points regulating flow into and out of the area. Thus, the demand volumes will never actually be reachecL 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 transit. Thi-~ adjustment in travel schedules, which could be reinforced with r~mp 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 I;ateway trips have been removed from the assigned traffic vol-mes. This is a major ass-mption. TVTC has agreed to treat the Altsmont Pass, Vasco Road, Crow Canyon Road to Castre Valley, Dublin Grade, Sunol Grade, and 1-680 north as physical gateways. It is unrealistic to plan local transportation facilities 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 unconstrained trafc volumes have been developed for the Tri-Valley network. The constrained traffic volnmes 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 trsfc, and on Figure 5-5 for the 'gateway constrained" traffic volumes. The constrained voh~mes are considered the baseline volumes. In order to develop rational action plans 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 LO. 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 ~'acilities management agreements in terms oJ~ rnrnp metering and freeway surveillance and control, which would fairly apportion avajJable capacity in such a way that LOS F wll] be avoided except for unavoidable traffc incidents which create intermittent blockages of capacity. Barton-Aschman Associates, Inc. 77