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Generally, the lower the number of stops the better the timing plan

"Signal timing and Coordination Strategies Under Varying Traffic Demands" (2012)

Nevada Department of Transportation, Report No. 235-11803


Stop rate is the average number of stops a driver has to make while driving along the entire arterial.

Stop rates are directly related to CO2 emissions. The more times the vehicle stops the more CO2 its internal combustion engine emits.

That happens because every stop is followed by acceleration, which contributes to CO2 emissions more than any other of four driving modes.

Bar graph of emissions in different modes
Offsets on a time-space diagram

Gray strips correspond to the share of cars passing through the (i-1)-th intersection but forced to stop at the i-th one.

Coordination itself does not guarantee minimal stop rate.

There is usually more than one set of offsets providing a particular pair of bandwidths. We can shift the green time intervals within certain limits at some intersections, without changing the bandwidths. With that, we change the stop rate.

This way we can reduce it by half or even more sometimes.

GTS minimizes average vehicle stop rate by means of an embedded Dynamic Programming algorithm 

Tunnel exit in Sofia
Comparison of the inbound and outbound traffic flows during the day

   The ratio between two opposite traffic flows changes during the day.

    By changing offsets accordingly to the current situation in such a way as to minimize average stop rate we reduce emissions substantially.

For this example calculations show:

Comparison of the stop rate and CO2 emissions in Sofia with and without application of Green Traffic Software
Busy street in Sofia
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