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 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)

Support. There are locations where, due to changes in the traffic conditions, the need for a traffic signal is no longer present. Several obvious locations would be where a school or commercial development has a signal at an entrance and the facility has closed or relocated. It is also possible traffic signals at intersections of public streets can no longer be justified due to changes in traffic patterns, such as new roadway construction or changes in the neighborhood. In any case, it can be a very difficult decision to remove an existing signal.

If the removal of an existing traffic signal is to be successful, misperceptions by the general public are among the greatest hurdles to overcome. While these can be very high hurdles, they are possible to clear if the proper engineering considerations are made and supported.

The removal of an unwarranted signal can result in cost savings to the public, that includes: reduced delays, reduced energy and fuel consumption and reduced emissions. Quantifying the annual savings to the public might help with the removal of the signal.

Guidance. There are four major considerations that should be reviewed before the removal of an existing signal: warrants, crash experience, sight distance and pedestrians.

A. Warrants. If traffic volumes are so that the highest activity day is only 50 percent of the required volumes to meet any of the MUTCD warrants, then removal can be considered. For example, Warrant 1 requires 150 side street vehicles per hour for any eight hours of an average day to be considered warranted. If there are 75 or fewer this would not be considered a warranted hour. If none of the hours of a normal day meet this level, then the signal could be a candidate for removal. Care must be taken when evaluating the main-line volumes because if they are at or are significantly higher than the warrant requirements, removal could be more difficult.

B. Crash Experience. Crash experience, both historical and expected, can be a very tough issue when considering a signal for removal. A thorough review of the crash history at the intersection is to be done to determine what has been occurring at the intersection. Historically, the removal of an unwarranted signal can cause a 90 percent decrease in rearend type collisions, a 30 percent increase in right angle crashes, 10 percent increase in left turn crashes, and 10 percent increase in pedestrian crashes.

The nature of the crashes that could be expected after the removal of the signal is influenced by the type of control that will replace the signal. If a multi-way stop is used then, in general, an increase in crashes would not be expected. If, however, a two-way stop control is planned then the percentage changes described above can be expected.

Regardless of the traffic control that is planned after the signal is removed, a detailed before/after review is to be documented.

C. Sight Distance. The sight distance available to the side street, particularly if two-way stop control is proposed, is very important to the removal decision. If the sight distance available for the side street is less than the stopping sight distance for the mainline approach speed, signal removal should not be considered without providing for the recommended sight distance.

D. Pedestrians. Consideration for pedestrians using the existing signal must be made using appropriate warrants. If a signal is removed, alternate pedestrian accommodations should be considered.

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.