Glossary of Terms for Transportation, Traffic and Signalization- Chapter 3

Guard Time: Unused time by a traffic at intersection between phases. In other words, the time which vehicles pass through safely that enters the intersection at yellow time before the green light up to the crossing flow.

Protected Return: Allowing to turn right and left without causing collision of vehicle or pedestrian flow

Critical Speed: The speed value at which capacity is formed for a highway facility.

Vehicle Queue: A vehicle, bicycle, or person waiting to receive right of way at an intersection. Slowly moving vehicles or vehicles joining the back of the queue are also included in the number. A fast-moving group of vehicles is referred to as a movable queue or a cluster of several.

Queue Discharge: Discharging of the vehicles at the queue which is high density and low speed flow.

Cluster: A group of vehicles or pedestrian travel as a group by chance or deliberately due to signal control, road geometry, standing or other factors.

Cluster Ratio: It is a useful parameter in measuring the type of arrival. This ratio is calculated by dividing the proportion of all vehicles coming to the green by the movement in question. (g/C)

Allowance Return: Left or right turns against vehicle or pedestrian flows at signalized intersections.

Bus: Wheeled vehicle type that carry significant number of passenger (at least 16 people), designed to travel urban areas and highways.

Bus Stop: The area where public transport takes off and put passengers on. It contains one or more loading areas and can be in-line or out-of-line.

Bus Lane: It is a priority road lane reserved for buses at certain times of the day or days of the week. Under certain circumstances, it may also be used by other vehicles, such as taxis and motorcycles, to make a right-left turn or in situations that meet the requirements of traffic laws.

Automobile Unit Equivalent: The equivalent of the number of passenger vehicles in a vehicle under specified road, traffic and control conditions.

Pre Time-Control: It is a signal management mode predetermined the phase plan, cycle length and phase duration, where the times do not change and are repeated continuously according to the demand from any sensor.

Private Return Lane: Especially determined for right and left return movements. Private lanes used by the vehicles that will make these turns.

Pelican Pedestrian Crossing: It is the passage which painted as vertically and where the pedestrians have right of way at intersection points.

Performance Measurements: Quantitative and qualitative features which defined the service quality served by a transportation facility.

Free Flow: Traffic flow that is not affected by any conditions.

Free Flow Speed: (1) The theoretical speed of traffic, which occurs when there is no vehicle. (2) The average speed of vehicles traveling on a highway under low volume conditions.