Timing Table:

A set of phases represents the timing table for a pretimed controller. Each phase is further divided into control intervals. For traffic signals at intersections, three intervals are typically used: green, yellow and red clearance. Each control interval represents a period of time during which states of all signals remain constant. The data items describing a control interval are length of the interval and a vector of signal states. The length specifies the time duration of the interval and the signal states specify the right-of-way for various turning movements. The number of bits required to represent each signal state variable is equal to Number of egress links. Each 4 bits of this variable represents the right-of-way for a particular movement, and may have the following values:

0

Blank: The signal is not used (no regulation for the movement);

1

Red: Movement is not allowed or vehicles should stop before moving again (i.e. flashing red, see below);

2

Yellow: Vehicles should prepare to stop if time headway from the signal is longer than a threshold;

3

Green: The movement is allowed.

One of the following two tags can be added to a signal ``color value'' to indicate whether the movement is protected or has a lower priority.

4

Arrow: The movement is protected;

8

Flashing: The movement has a lower priority.

   

Table 4-1: An example of pretimed signal plans (see Figure 4-5)

Phase	Control Interval		Signal State
	Diagram	Length (sec)	40	20	30	10
1		9	111	113	333	111
		3	111	112	222	111
		1	111	111	111	111
2		15	111	111	111	333
		3	111	111	111	222
		1	111	111	111	111
3		17	111	333	111	113
		3	111	733	111	112
		1	111	333	111	111
4		18	333	333	111	111
		3	222	222	111	111
		1	111	111	111	111

Blank out sign is represented by a special state value (i.e. F). States for other types of signals and signs are represented either by cardinal values (e.g. VSLS) or dedicated integer codes (e.g. message signs).