902.2 Traffic Control Signals (MUTCD Chapter 4B)

902.2.1 General (MUTCD Section 4B.01)

Support. Words such as pedestrians and bicyclists are used redundantly in selected Articles of EPG 902 to encourage sensitivity to these elements of “traffic.”

Standards for traffic control signals are important because traffic control signals need to attract the attention of a variety of road users, including those who are older, those with vision disabilities, as well as those who are fatigued or distracted, or who are not expecting to encounter a signal at a particular location.

902.2.2 Advantages and Disadvantages of Traffic Control Signals (MUTCD Section 4B.02)

Support. When properly used, traffic control signals are valuable devices for safety and the control of vehicular and vulnerable road user traffic. They control the various traffic movements by alternating between directing them to stop and permitting them to proceed and thereby profoundly influence traffic flow. This accomplishes the need to safely separate road users in time in order to prevent crashes.

Traffic control signals that are properly designed, located, operated, and maintained will have one or more of the following advantages:

A. They reduce the frequency and severity of certain types of crashes, especially right-angle collisions and those involving vulnerable road users.

B. They provide for the orderly movement of traffic.

C. They increase the traffic-handling capacity of the intersection if:

1. Proper physical layouts and control measures are used, and
2. The signal operational parameters are reviewed and updated (if needed) on a regular basis (as engineering judgment determines that significant traffic flow and/or land use changes have occurred) to maximize the ability of the traffic control signal to satisfy current traffic demands.

D. They are coordinated to provide for continuous or nearly-continuous movement of traffic at a definite speed along a given route under favorable conditions.

E. They are used to interrupt heavy traffic at intervals to permit other traffic, vehicular or pedestrian, to cross.

Traffic control signals are often considered a panacea for all traffic problems at intersections. This belief has led to traffic control signals being installed at many locations where they are not needed, adversely affecting the safety and efficiency of motor vehicle, bicycle, and pedestrian traffic.

Traffic control signals, even when justified by traffic and roadway conditions, can be ill-designed, ineffectively placed, improperly operated, or poorly maintained. Improper or unjustified traffic control signals can result in one or more of the following disadvantages:

A. Excessive delay,

B. Excessive disobedience of the signal indications,

C. Increased use of less-adequate routes as road users attempt to avoid the traffic control signals, and

D. Significant increases in the frequency of collisions (especially rear-end collisions).

902.2.3 Alternatives to Traffic Control Signals (MUTCD Section 4B.03)

Guidance. Since road user delay and the frequency of some types of crashes are sometimes higher under traffic signal control than under STOP sign control, consideration should be given to providing alternatives to traffic control signals even if one or more of the signal warrants (see EPG 902.3) has been satisfied.

Option. These alternatives may include, but are not limited to, the following:

A. Installing signs along the major street to warn road users approaching the intersection;

B. Installing a roundabout to reduce fatal and serious injury crashes and vehicular conflicts that result in fatal and serious injury crashes (see EPG 913.1.12 if the location is in close proximity to a grade crossing);

C. Installing a pedestrian hybrid beacon (see EPG 902.10), rectangular rapid flashing beacons (see EPG 902.12), pedestrian-actuated Warning Beacons (see EPG 902.18), or In-Roadway Warning Lights (see EPG 902.20) if pedestrian safety is the major concern;

D. Relocating the stop line(s) and making other changes to improve the sight distance at the intersection;

E. Installing measures designed to reduce speeds on the approaches;

F. Installing a flashing beacon at the intersection to supplement STOP sign control;

G. Installing flashing beacons on warning signs in advance of a stop-controlled intersection on the major-street and/or minor-street approaches;

H. Adding one or more lanes on a minor-street approach to reduce the number of vehicles per lane on the approach;

I. Revising the geometrics at the intersection to channelize vehicular movements and reduce the time required for a vehicle to complete a movement, which could also assist pedestrians;

J. Revising the geometrics at the intersection to add pedestrian median refuge islands and/or curb extensions;

K. Installing roadway lighting if a disproportionate number of crashes occur at night;

L. Restricting one or more turning movements, perhaps on a time-of-day basis, if alternate routes are available;

M. If the warrant is satisfied, installing multi-way stop control;

N. Employing other alternatives, depending on conditions at the intersection.

Support. EPG 233.5 contains information on intersection alternatives.

902.2.4 Basis of Installation of Traffic Control Signals (MUTCD Section 4B.04)

Support. A careful analysis of traffic operations, pedestrian and bicyclist needs, and other factors at a large number of signalized and unsignalized locations, coupled with engineering judgment, has provided a series of signal warrants, described in EPG 902.3, that define the minimum conditions under which installing traffic control signals might be justified.

MoDOT’s general policy is to own, operate and maintain all traffic signals and flashers installed or constructed on the state highway system.

When the installation of a traffic signal is warranted, the cost of the signal (excluding emergency and school signals), installation and maintenance, and electrical power for operation, unless otherwise stated, will be borne by the Commission. Where possible, MoDOT takes advantage of any reduced power rates by including in the municipal and/or county agreement a phrase the city will pay for the power, with reimbursement to be made by the state. Where city/county power is not available, MoDOT pays for the power directly.

The need for signalizing an intersection will normally be recognized and initiated at the district level. A careful analysis of traffic operations, pedestrian and bicyclist needs, and other factors at a large number of signalized and unsignalized locations, coupled with engineering judgment, has provided a series of signal warrants, described in EPG 902.3, that define the minimum conditions under which installing traffic control signals might be justified.

Meeting the warrant requirements of the MUTCD alone is not necessarily a sufficient reason to install traffic signals. Since the installation of traffic control signals will operate either to the advantage or disadvantage of vehicles and persons controlled, the selection and use of traffic control devices is to be preceded by a thorough engineering study of the roadway and traffic conditions.

Guidance. The design (including the phasing, operation, and timing) of new traffic control signals should be based on an engineering study of roadway, traffic, and other conditions.

902.2.5 Basis of Removal of Traffic Control Signals (MUTCD Section 4B.05)

Guidance. Engineering judgment should be applied in the review of operating traffic control signals to determine whether the type of installation and the timing program meet the current requirements of all forms of traffic.

If changes in traffic patterns eliminate the need for a traffic control signal, consideration should be given to removing it and replacing it with appropriate alternative traffic control devices, if any are needed.

If the engineering study indicates that the traffic control signal is no longer justified, and a decision is made to remove the signal, the removal should be accomplished using the following steps:

A. Determine the appropriate traffic control to be used after the removal of the signal.

B. Remove any sight-distance restrictions as necessary.

C. Inform the public of the removal study.

D. Flash or cover the signal heads for a minimum of 90 days, and install the appropriate STOP sign control or other traffic control devices.

E. Remove the signal if the engineering data collected during the removal study period confirms that the signal is no longer needed.

Option. Because Items C, D, and E in the third guidance paragraph of this Article are not relevant when a temporary traffic control signal (see EPG 902.4.11) is removed, a temporary traffic control signal may be removed immediately after Items A and B are completed.

Instead of total removal of a traffic control signal, the poles, controller cabinet, and cables may remain in place after removal of the signal heads for continued analysis.

Standard. After all of the above considerations have been evaluated and if the decision is made to proceed with the removal, the following steps shall be taken:

1. Central Office Traffic shall be advised and documentation of the above noted evaluations provided to support the decision.
2. Public notice of the intention to remove shall be made. This can consist of news releases, public hearings and presentations at city council meetings or canvassing parties affected by the removal. This is a very important step and the district must be prepared to answer any questions that might arise.
3. Establish a date for the signal to be turned off and notify Central Office Traffic.
4. Flash the signal heads for a minimum of 30 days. After the flash period, cover the signal heads for no less than 60 days. The type of flash used shall compliment the type of traffic control selected for the intersection, yellow/red for two-way stops and red/red for four-way stops.
5. After the 90 day transition period has been successfully completed, the physical removal of the signals can be initiated. A comprehensive removal shall be completed with all concrete foundations and bases removed to at least flush with the ground. Consideration shall be given to filling or securing any pull boxes.

Guidance. When a temporary traffic control signal is removed the appropriate traffic control to be used after removal of the signal is to be determined and any sight distance restrictions removed.