Traffic Engineering CENG 3101 - Chapter 5

Used to mark the end of a roadway in areas other than construction or maintenance.

Warns road users of an obstruction by using alternating black and yellow stripes.

Three yellow retro reflectors arranged horizontally or vertically on a white panel.

Nine yellow retro reflectors placed on a yellow or black diamond panel.

Inform road users of specific traffic laws and regulations.

Warn drivers about hazards along the route.

Provide guidance to travelers, including directions and destinations.

Signifies a prohibition of the movement indicated by the symbol.

The smallest unit of time within a signal cycle where the signal indication remains unchanged.

The time during which the signal is yellow, allowing vehicles that cannot safely stop to enter the intersection.

The time after the yellow light, when all signal lights are red, allowing vehicles that legally entered on yellow to clear the intersection.

The time during which the signal is green, allowing traffic to move through the intersection.

The time during which the signal is red, prohibiting traffic from moving through the intersection.

The time delay between the beginning of a green phase at one intersection and the beginning of a corresponding green phase at the next intersection.

A set of traffic signal movements that are executed together, allowing non-conflicting movements during green intervals.

Markings parallel to the direction of travel. Examples include centerlines, lane lines, and pavement edge lines.

Markings that cross the direction of travel. Examples include stop lines and crosswalks.

A single broken line, used on roads with two lanes in the same direction, indicating passing is permitted.

A single solid line, used on roads with two lanes in the same direction, indicating passing is discouraged, but not prohibited.

A double solid line, used on roads with two lanes in the same direction, indicating passing is prohibited.

A white lane line used to separate lanes of traffic in the same direction. (A single dash indicates passing is allowed; a solid line indicates passing is discouraged; two solid lines indicate passing is prohibited)

A yellow or white line used to indicate the edge of a rural road where there are no curbs. This line should be at least 150mm from the actual edge.

Too many warning signs can make drivers ignore them, reducing their effectiveness.

Guide/Informative signs provide directions, destinations, services, and other important information for drivers.

The Manual on Uniform Traffic Control Devices (MUTCD) provides guidelines for various types of signs, including guide signs.

A traffic signal cycle is a complete sequence of red, yellow, and green lights, indicating different traffic movements.

The time it takes for one complete traffic signal cycle is known as the cycle length.

A traffic phase is part of a cycle dedicated to a specific traffic movement, like turning left, going straight, or pedestrians crossing.

Signal timing is designed to minimize delays, improve traffic flow, and ensure safe movement of vehicles and pedestrians.

A signal phase is a period that allows a set of movements to flow and safely halt before another set of movements. It consists of a green interval, the change interval and the clearance interval. The change and clearance intervals make sure that all vehicles in the previous phase have cleared the intersection. A green interval allows a set of movements to flow.

A specific point in a signal phase where a designated movement or set of movements is allowed to start and then safely stopped before another set of movements is permitted.

A type of traffic signal phasing where one lane group gets green light and the other lane group gets red light simultaneously. This is used to ensure that conflicting flows do not happen.

One part of a phase that is set apart from the primary movement. In effect it is a special phase that relates to a parent phase. For example, a pedestrian phase may have a split phase to allow for safe pedestrian crossings within a larger phase.

A measure of the variability of demand during the peak hour. It's calculated by dividing the volume during the peak hour by four times the volume during the peak fifteen minutes within that peak hour.

The peak hour volume divided by the peak-hour factor. The DHV reflects the traffic volume during the busiest hour of the day.

One or more lanes on an intersection approach that have the same green phase. This means the lanes are treated as a group for traffic signal control.

The lane group within a traffic signal phase requiring the longest green time. This is important for designing efficient traffic signal phases.

The total time wasted during each cycle due to factors like start-up delays, amber time, and pedestrian walk time.

The amount of time within a cycle that is available for vehicles to move through the intersection, excluding the lost time.

The maximum number of vehicles that can pass through an intersection during a specific period, usually an hour, given optimal conditions. It's a key factor in traffic planning and signal design.

The time needed for a queue of vehicles to clear a signalized intersection during a green phase. It's a factor that influences cycle length calculations.

A method for determining the ideal cycle length of a traffic signal, aiming to balance the needs for green time and minimizing delays for all lanes.

The minimum green time required for a phase before considering the volume of traffic. It's often determined by pedestrian needs and crossing times.

A design process that involves several critical steps. They include phase design, amber and clearance time determination, cycle length calculation, green time allocation, pedestrian crossing needs, and performance evaluation of the final design.

The total time spent in each cycle dedicated to transitioning between green, yellow, and red phases. It includes amber time, clearance time, and other factors.