Assessment of optimality of arterial signal timing plans under diurnal and day-to-day variations in traffic demand

Most U.S. urban traffic signal systems deploy multiple signal timing plans to
account for daily variability of traffic demand (i.e. morning peak, midday, afternoon
peak, off peak and night). Groups of signals (belonging to the one zone or section) along
an urban arterial, usually operate in a coordinated manner. This essentially means that
timing plans change at the same time for all the signals in the group, so as to facilitate
vehicle progression of through a series of signals. Good traffic signal timing practices
assume a certain level of monitoring and maintenance in order to guarantee that they are
efficient in servicing current traffic conditions.