britt-allen
commented
6 months ago D = F (TT - TT_t) = F (L/V - L/V_t)
Is this one formula or two? @kengodleskidot
I see this was copied and pasted from here. I am just confused because the following text says these formulas but it look slike a long one that equals the other??
The Delay performance metric is the amount of additional time spent by the vehicles on a section of road due to congestion. This is the difference between the travel time at a non-congestion speed and the current speed. The congestion, or threshold, speed is usually 35MPH but in PeMS we compute the delay for a number of different thresholds so that we can accommodate different definitions of delay. The threshold values used are 35, 40, 45, 50, 55, and 60 MPH. The formula for this is simply D = F (TT - TT_t) = F (L/V - L/V_t). In these formulas, D is delay, TT is the travel time, TT_t is the travel time at the threshold speed, F is the flow, L is the length of the segment, V is the current speed and V_t is the threshold speed. Note that by definition, delay can never be negative.
We compute Delay for the various threshold values at the 5-minute level for each loop detector location (lane) as well as across all lanes at a given station. The measure of Delay can be summed up across time and space. This makes it quite easy for us to aggregate these measures to larger geographical regions and longer temporal periods.