Using desired speed to modify desired speed decisions
You can permanently change desired speeds with DesSpeedDecisions (desired speed decisions), for example on highways, for traffic signs which limit the speed, or at the entry and exit of a town. Desired speed decisions are placed at the position in the network where the change is to begin. For multi-lane links, position a desired speed decision on each lane and define its attributes.
With desired speed decisions, a vehicle only reduces its speed once it has entered a desired speed decisions section. The vehicle is then assigned a new desired speed and changes its speed accordingly. To do so, it uses the desired acceleration or desired deceleration.
When entering the network, each vehicle is assigned a fractile value for speed distribution. This value remains unchanged during the entire simulation time. If this value is 40 %, the vehicle is always assigned a 40 percentile of the desired speed distribution for desired speed decisions. If the fractile is 100 %, the vehicle is always assigned the highest distributed speed.
Delay measurement for the desired speed decision
After the vehicle has traversed the desired speed decision, Vissim calculates a theoretical speed over several time steps until this speed is identical with the new desired speed of the vehicle. This theoretical speed starts at the original desired speed and ends at the new desired speed. During the time steps the vehicle needs to reach its new, desired speed, Vissim compares the current speed of the vehicle with the current theoretical speed calculated - not with the new desired speed the vehicle is supposed to reach - in order to create a basis for delay measurement calculation.
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