Question

produce a (250 words min) report that describes the different stages o the signaling design process an how the information provided by signalling design is used by installation maintaince and/or testing

Answer 1

Traffic control signals are signaling devices that are positioned in a way to control or direct the flow of traffic. Some examples of traffic control devices are 3 section signal heads, advanced warning flashers, school flashers, overhead beacon flashers, and pedestrian hybrid beacons. It should be noted that all traffic control devices require a permit.


Different Stages of Signal Design Process :-

The following list is provided as a general representation of the stages that should be taken when designing traffic signals. This list is only provided as a guide and not as an all-encompassing checklist.

 Obtain Project Background & Design Data

 Prepare Survey/Base/Existing Plan
 Initial Site visit (where applicable)
 Identify Signal Requirements / Verify with TE reports where applicable
o Left turn phasing
o Pedestrian phases
o Overlaps
o Preempts
o Turn restrictions

 Review Geometric Design
 Establish crosswalks, stop lines and review ramp locations
 Identify overhead structure support (span wire/mast arm)
 Locate Signal heads (vehicles/pedestrian) and push buttons
 Locate Signal Poles
 Identify detection method and locate vehicle detectors
 Locate cabinet and power source
 Locate Pull boxes and conduits
 Locate and determine sign requirements
 Locate and design signal interconnect if applicable

Maintenance :-

Maintenance practices should include the following:

Response time - Response time depends on two factors - time to obtain an indication of failure and time to respond after receiving an indication of failure. The following requirements apply:

• Time to obtain indication of failure – Since closed loop systems and other centrally monitored systems provide an indication of controller failure, rapid failure identification can be accomplished using such techniques if these systems are supervised. Criteria for the percentage of failures that are initially detected within the traffic agency (as compared to reports from police, other agencies or citizens) are:

o For systems in excess of 400 intersections 70% of failures should be detected by the operating agency. In a dense network of coordinated signals, critical failure detection by the agency should approach 100%.

o For systems with 400 intersections or fewer, 50% of failures should be detected by the operating agency. Detection should be considerably higher for a dense network

• Time to respond after receiving an indication of controller or signal failure. o Within one hour during business hours. o Within two hours during non-business hours.

The Traffic Signal Report Cards indicate that a significant number of agencies conform to this requirement.
A procedure to identify the level of criticality for the intersection with respect to safety and congestion should be developed. Response priorities should be developed in accordance with this procedure.

Rates of critical failures (e.g. controller failures, deficient cabinet or signal wiring, short circuits, lightning strikes, etc.) should not exceed F failures per year per for each intersection. Where this rate is exceeded for a period of one year, an investigation to determine the root cause should be conducted. To establish the value of F, intersection failure rates should be reviewed and the value of F set at the highest 20% of intersection failure rates.

​​​​​​​Spares for the current equipment in the field should always be available.