However, this also occurs for links that represent a turn bay, which is inappropriately pessimistic. Therefore, for turn bay links that may possibly experience temporary oversaturation, it is appropriate to use record type 291 to tell the model to reduce saturation flow rates for the adjacent link instead of the upstream links. However, under severely oversaturated conditions, measurements of delay, stops, and fuel consumption are known to become less accurate, thus compromising the effectiveness of the DI objective function. Similarly, under severely oversaturated conditions, increases in progression opportunities may not address spillback problems, thus compromising the effectiveness of the PROS objective function. The new objective functions involve throughput and queuing ratio.
Most users accept the default optimization step sizes within the program.
However, sometimes the use of alternative hill-climb optimization step sizes , available on record type 4, can provide better results. In order to access the latest features of the program, it is necessary to edit the input file so as to request step-wise simulation. This simply requires a negative sign on record type 5X. Release 8.1 implements the 1994 HCM delay equation for signalized intersections, whereas releases 8.2 and higher implement the 1997 delay equation . For example, an output parameter called Flow indicates the number of vehicles discharged during simulation. For a given link, if Flow is lower than the input volume, this may indicate inadequate capacity due to spillback, or possibly insufficient green time.