SIGNALIZATION
Alf Badge., P.E. Senior Engineer Post-Buckley-Schuh-Jernigan, Inc Charlotte, North Carolina
Charles V. Zegeer, P.E. Associate Director of Roadway Studies Highway Safety Research Center University of North Carolina Chapel Hill, North Carolina
FIGURE 5-1 Pedestrian signal displays.'
Traffic Signals Traffic signals are intended to assign the right-of-way to vehicular and pedestrian traffic. When installed appropriately, traffic signals can provide many benefits, including the interruption of heavy volumes of motor vehicles where there are insufficient gaps in motor vehicle traffic for pedestrians to cross safely at intersections or midblock locations. Unwarranted or improperly used traffic sig-nals can cause excessive delay for pedestrians and motor vehicles, signal disobedience, and an increase in certain accident types. Even where warranted, traffic signal installations commonly result fn an increase in rear-end and total accidents, with a corresponding reduction in more severe right-angle acci-dents. The effect of traffic signal installations on pedestrian accidents is not well known, but different locational characteristics of the sites are important factors in the accident experience at signals.°
While many traffic signals include only the green, yellow, and red signal faces, a variety of signal lens faces may be used, depending on needed signal phasing. Studies have suggested, however, that highly-com-plex, multiphase signals often result in con-fusion and hazardous situations for pedestrians. Therefore, in cases where such complex phasing is necessary, pedestrian sig-nals and other pedestrian improvements are strongly recommended' The Manual on Uniform Traffic Control Devices (MUTCD) provides eleven separate warrants for installing new traffic signals.'
■ Warrant 1—Minimum vehicular volume
■ Warrant 2—Interruption of contin-uous traffic
■ Warrant 3—Minimum pedestrian volume
• Warrant 4--5chool crossings
• Warrant 5—Progressive movement • Warrant 6--Accident experience
• Warrant 7—Systems • Warrant f3—Combination of warrants
• Warrant 9—Four-hour volumes
• Warrant 10—Peak-hour delay • Warrant 11—Peak-hour volume

Note that warrant numbers 3 and 4 relate direct-ly to pedestrians, and warrant number 6 also mattes some reference to pedestrian considera-tions. Studies have found that only a small per-centage of new traffic signals have been installed M the United States based primarily on pedestri-an considerations. However, recent revisions in the minimum pedestrian warrant (warrant 3) are expected to result in easier justification of traffic signals based on the needs of pedestrians.', The revised minimum pedestrian volume warrant states that a traffic signal may be war ranted when the pedestrian volume crossing the major street at an intersection or midblock loca-tion during an average day is either (1) 100 or more for each of any four hours, or (2) 190 or more during any one hour. These volume require-ments can be reduced by as much as SO percent when the predominant crossing speed is below 3.5 feet per second (1.1 mph), for example, as would often be the case with older pedestrians. In conjunction with these volumes, there shall be less than 60 gaps per hour in the traffic stream of adequate length for pedestrians to cross during the same period.0
Pedestrian Signals Pedestrian Indications Pedestrian signals include the symbolic man/hand symbol (recommended in the MUTCD) or the WALK/DON'T WALK word message (accepted alternative in the MUTCDP in conjunction with traffic signals at many locations. The steady DON'T WALK or steady hand message indicates when pedestrians should not belt the crosswalk. The flashing DON'T WALK or flashing hand sym-bol are clearance intervals, that is, pedestrians should not step into the crosswalk, but they may finish crossing if they are already in the crosswalk (i.e., DON'T START). The WALK or walking man symbol indicate that pedestrians may cross the street in the direction of the signal.' Pedestrian signal displays are illustrated in figure 5-1. In the past, MUTCD allowed the flashing WALK as an option to the steady WALK indica-tion. Some agenCies used the flashing WALK at some locations to indicate to pedestrians that they should watch out for tuming vehicles, whereas a steady WALK was used at other lace-tions where no turning vehicles are permitted across the crosswalk (e.g., on the approach of a one-way street). However, since January, 1991, the flashing WALK Indication has been taken out of the MUTCD. It is recommended that the flash-ing WALK message no longer he used and Instead be converted to the steady WALK. Further, the symbolic (man and hand) pedestrian messages are suitable alternatives to the WALK and DON'T WALK word messages, and either word or sym-bolic messages are acceptable,' The absence of pedestrian signals at some signalized intersections can create a barrier to pedestrians wishing to cross the street. It may force some pedestrians to take unnecessary risks to cross traffic. This is particularly critical to the two age groups with the most difficulty crossing streets. Children do not possess the experience and judgment to recognize the inherent dangers, and their vision and depth perception have not fully developed to provide accurate infonnation. Older pedestrians may possess limited stamina to cross traffic and declining hearing and vision to recognize and respond to conflicts. It has been well documented by Federal Highway Administration (FHWA) sponsored research activities that many pedestrians do not understand the meaning of the pedestrian signals and indications, particularly the flashing DON'T WALL° These problems highlight the need for more effectively educating pedestrians—to include distribution of educational materials and signing at schools, such as the un-streel RI 0-2A "CROSS ONLY ON PEDESTRIAN (SYMBOL) SIGNAL. and the R10-413 "PUSH BUTTON FOR (PEDESTRIAN SYMBOL). signs. An additional pedestrian education sign has also been used as shown in figure 5-2,s although not yet incorpo-rated into the MUTCD. In addition to education-al signs, educational flyers and brochures are recommended in cities or areas where pedestrian violations are a problem.

Besides a lack of understanding, some pedestrians violate the signals because of their impatience or other reasons (figure 5-3). Motorists often put pedestrians at risk when they run red lights or make right and left turns while failing to yield the legal right-of-way to pedestri-ans. Police enforcement is often the best solution for these problems.
Wan-ants for Pedestrian Signal Indications'
The MUTCD contains four recommendations for the installation of pedestrian signal indications:, 1. when waffle signals are Installed based on meeting the minimum pedestrian volume or school crossing warrants; 2. when an exclusive pedestrian interval is provided (i.e., with all conflicting vehicular traffic being stopped); 3. when the vehicle signals are not visible to pedestrians such as at one-way streets or "T. intersections); 4. at signalized intersections within estab-lished school crossing locations. Pedestrian signal indications are recom-mended when there are: multiphase signals; com-plex geometry (more than four legs, wide streets, refuge islands); areas where compliance is high; areas where older adults or young children are present; or pedestrian push-buttons are in use! Section 4B-28 of the MUTCD on "Provisions for Pedestrians,. describes three spe-cific conditions that must be considered:'
1) Signal indications must be visible to pedestrians. This can be accomplished for a given pedestrian movement by a) provision of pedestrian indica-tions; b) a red-yellow-green signal face for an adjacent vehicular movement visible to pedestrians; or c) vehicular indications for conflict-lng movements that can be conve-niently viewed by pedestrians, and from which pedestrians can readily and accurately deduce when they have the right-of-way.
STEADY
elWATCH FOR TURNING CARS
START CROSSING
FLASHING
DON'T START
IIII FINISH CROSSING IF IN CROSSWALK
STEADY WAIT ON CURB
DON'T CROSS
TO CROSS
PUSH BUTTON •
FIGURE 5-2. Example of an educational sign for pedestrian signal display.
2) There must be an opportunity to cross without undue delay. Pedestrian actua-tion shall be installed at traffic control signals where the signal operation does not otherwise provide this opportunity. 3) Pedestrians should be pmvided with suf-ficient time to cross the roadway. This may be accomplished by adjusting the signal operation and timing to automati-cally provide this assurance via pedes-trian actuation.
Visibility of Devices Most state statutes require pedestrians to obey the vehicular traffic signals when pedestrian sig-nals are not present. Frequently, the vehicular signal heads are not visible because of the geom-etry and the signal equipment used. Pedestrian lack of compliance with traffic signal indications can be traced partly to a lack of visibility. It is recommended that pedestrian signal Indications be provided when the pedestrian can-not see the vehicular signals to determine the right-of-way (figure 5-4). This would include situations when diagonal spans, optically pro-grammed signal heads, or tunnel visors are used. In addition, many sight-impaired or elderly pedestrians cannot see the pedestrian signal heads across wide streets (e.g., 75 feet or wider). Thus, pedestrian signals may be neces-sary in the medians of such wide streets. Other conditions are described in the section on design considerations.
Pedestrian Signal Timing The MUTCD recommends at least a 4- to 7-sec-ond walk interval (figure 5-5). However, at some intersections, this may present a dilemma to pedestrians who see a DON'T WALK display before they are more than one or two lanes across the street. In actual practice the pedestri-an almost always continues forward rather than return to his or her starting point. It would be very desirable to provide a longer WALK interval at some locations if possible. The fifteenth percentile walking speed should be used for setting the design walk speed where there is a high proportion of elderly pedes-trians. In the absence of a specific study this would be between 3 and 4 feet per second, depending on the presence of slower pedestrians.
Pedestrian Push-Button
At locations where pedestrian activity is infre-quent and pedestrian signal phasing is not warranted on a full-time basis, the use of pedes-trian-actuated signals (i.e., push-buttons) may be justified (figure 5-6). Pedestrian push-buttons are appropriate where occasional pedestrian movements occur and adequate opportunities do not exist for pedestrians to cross.' Where no pedestrian signals are present, actuation of the push-buttons may be used to extend the green phase to allow pedestrians sufficient crossing time. Push-buttons may also be used with pedes-trian signals to provide a quicker WALK interval with extended WALK time for safer pedestrian crossing? Pedestrian push-buttons should be mounted 3 to 4 feet above the sidewalk and placed in a conspicuous, convenient location,' preferably next to curb ramps. Such placement will reduce the need for signing to explain which button needs to be pushed to cross the street. Signs such as PUSH BUTTON FOR WALK SIGNAL are needed with the actuation devices to explain their meaning and use. When two actuation devices are placed close together for crossings in different directions le.g, at intersections), it is important to indicate which crosswalk signal is controlled by each push-button (e.g., PUSH BUTTON TO CROSS SEC-OND AVENUE). Push-button devices may also be needed on medians and refuge islands where sig-nal timing does not allow pedestrians to cross the complete street width during one signal phase..
Pedestrian safety can be enhanced by pedestrian push-buttons only if they are correctly installed and maintained. Many agencies resist installing pedestrian push buttons because they are either infrequently used or often used improperly by pranksters wishing to disrupt traf-fic flow. Problems that have been identified con-tributing to pedestrian push-button nonuse include the following... • Many push-button devices are hidden front pedestiian view or out of mall such as on telephone poles 10 to 20 feet from the crosswalk).
• Signing is often nonexistent or confus ing and does not indicate which push-button corresponds to each crosswalk. • At many locations, timing requires that pedestrians wait one minute or more after the buttons are pushed before the WALK interval is displayed. Often, pedestrians push the button and cross the street before the WALK interval begins. Then traffic is stopped when no pedestrians are present. • Some plish.huttons are inoperative or operated only during off-peak hours (and pedestrians were not instructed that the push-buttons only worked dur-ing certain periods of the day). The following are recommendations to improve the effectiveness of pedestrian push-but-ton devices,
• Repair and maintain the push-buttons as necessary to make them more respon-sive to pedestrians (for example, time. them to provide a WALK interval to pedestrians within thirty seconds after the buttons are pushed). • Provide signs with push-buttons explain-ing the specific streets that should can be crossed when activated.
FiGURE 5-5. The MUTCD recommends at least a 4-to 7-second walk intenvul, but u lunyer interval , desirable. rIGURE 5-6. Pedestrian push-buttons ore often provided nt ksratinns with intermittent pedestrian volumes to call for the WALK message ond/or extend the crossing interval.

• Provide illuminated push-buttons similar to those used with elevators to indicate when the actuation device is opera-tional. These types of push-buttons reas-sure pedestrians that their signal call has been received by the controller. • Provide a si. explaining the opera. tional times at those pedestrian actua-tion devices that are designed to only operate at specific times of the day.
Left- and Right-Turn Phasing I hirty.seven percent of all pedestrian accidents at signalized intersections involve left- or right-turn-ing vehicles. One FHWA study found that the left turn vehicle-pedestrian accident rate was twice that involving right.turning vehicles, because of the increased obstruction of the driver's vision.' Potential solutions to pedestrian collisions ing right- or left-turn vehicles in some situations include the following: • design compact intersections with small turning radii that force slower speeds, • prohibit right-turn-on-red, ▪ use a separate left-turn phase (in co. (unction with a WALK/DON'T WALK signal). The prohibition of a turn movement may shift the problem to another location and have a very negative effect on capacity and delay. However, there are situations with heavy pedes-trian volurnes where left-turn prohibition may be justified.
Partial Crossings Walking distances at large intersections are often excessive. even for very mobile pedestrians. These walking distances require long WALK and flashing DON'T WALK clearance intervals. At heavily loaded intersections, especially with high volume left turns and four or more phases, the pedestrian timing requires a high percentage of the cycle length. This can lead to critical signal timing, resulting in intersection vehicle capacity deficiencies. Ideally, it is highly desirable for pedestrian convenience and compliance to cross an approach in one signal cycle. Where partial crossings exist, the following guidelines are rec-ommended:
I. Use raised channelizing islands (particularly for right's urn lanes) to reduce the curb-to-curb walking distance and signal cycle lengths. 2. Construct a median refuge island to reduce the walkinp, distance. This may require slow pedestrians to cross the approach dur-ing two signal cycles. Pedestrian push.but. tons would be installed on the median. Refuge Islands are vet y beneficial to the elderly and to the young; they can reduce pedestrian exposure to traffic. Ideally, median widths should be 10 feet or wider to provide enough space for pedestrians to stand. As mentioned in chapter 1, median refuge islands should be at least bees wide and in no case less than 4 feet wide.
3. Provide the necessary pedestrian crossing time and accept a reduced capacity for motor vehicle traffic.
4. As a last tenon, prohibit pedestrian move ments and direct them to a safer, nearby crossing location if the walking distances and signal timing are still unacceptable. It should be remembered, however, that the prohibition of a pedestrian movement can greatly increase the walking distance and time to cross the intersection. If the pedestrian move. ment across one approach of a four-legged inter-section is prohibited, then a pedestrian would have to cross the other three legs of the intersec-tion to reach the intended corner. This could increase the walking distance as much as 300 percent and the walking time by six to nine min-utes, and this may not be in strict compliance under ADA, which requires the provision of con. turnout routes for pedestrians. A balance is need-ed between the needs of motor vehicles and pedestrians.
Pedestrian Signals in a Coordinated Signal System Coordinated signal systems along a route involve timing the signals in sequence, so a motor vehi-cle may proceed at a constant speed and get a green light at each signal along the system. The use of pedestrian features in a coordinated sig-nal system can significantly influence the effec-tiveness of the signal system. It is not unusual to have signalized intersections, where the pedestrian timing exceeds those for its compan-ion vehicular movements because of malls times. The length of the WALK and DON'T WALK intervals can pose major limitations on the cycle length of the coordinated signal system. When the timing demands of the WALK and flashing DON'T WALK intervals are greater than the vehicle timing demand in concurrent pedestrian signal phasing, the resulting cycle lengths may be ninety seconds or greater. The limitations of sys-tem cycle lengths can significantly reduce the operation and flexibility of the system to respond to various traffic demands. One alternate timing scheme is to design the system timings without the pedestrian timing. Then, when the pedestrian push-buttons are activated, the local intersection is disconnected from the system for one cycle to service the pedestrian movement. This practice will degrade the effectiveness of the system if the pedestrian timing is activated frequently, since the system will consistently be transitioning into coordination. It is recommended to use one of the fol-lowing guidelines for handling motor vehicles and pedestrians in coordinated signal systems. I. Use actuated pedestrian signals when pedestrian volumes are light and when WALK times limit the vehicle movement timings. This will minimize the effect of the pedestrian signal timing on the opera-tion of the system. The pedestrian timing should be compatible with the system coor-dination timing or the system could be out of step as much as three cycles for each actuation.
2. Use fixed-time pedestrian signals with con-current pedestrian phasing and pretimed signals. Since the vehicular movements will be displayed every cycle, there is no bene-fit to actuating the pedestrian movements as they will be displayed concurrently with vehicular movements every cycle.
Pedestrian Signal Phasing Signal phasing operations exist that can reduce timing demand and improve signal system perfor-mance. The four alternatives below may be appropriate under certain situations, to handle the operation of a traffic signal for pedestrians and vehicles,' 1. Standard (or concurrent) timing involves a WALK indication that is displayed concur-rently with the green light for motorists, where motor vehicles may turn left or right after yielding to pedestrians. 2. The early release of pedestrian signal oper-ation displays red for the vehicular move-ments (particularly the right turn) while the WALK signals are displayed. The vehic-ular signals then get a ''green" indication. 3. The late release of pedestrian signal opera-tion displays the vehicular green indica-tions before display of the WALK indications.
4. Exclusive pedestrian phasing displays WALK signals without green indications for any vehicle movements.
S. Scramble pedestrian phasing incorporates a separate pedestrian phase where pedestri-ans are allowed to walk in any direction, including diagonally across the intersection. One method to evaluate these alternative phasing operations includes the conversion of all pedestrian and vehicular delay to "person delay,. by using an assumed auto occupancy rate. Often, concurrent pedestrian phasing produces mini-mum total delay. However, a study of accident data revealed that there was no significant differ-ence in accident rates for signals with no pedes-trian signals and those with concurrent pedestrian signal phasing, Thus, the installation of standard-timed pedestrian signals should not necessarily be expected to improve pedestrian safety at traffic signal'. intersections. At inter-sections with less than 1,200 pedestrians per day, there is no significant difference in pedestrian accidents between exclusive pedestrian signal phasing, concurrent pedestrian phasing, and no pedestrian signals..

The early release of pedestrian signal oper-ation always produces higher total delay. The late release of pedestrian signal operation produces higher total delay for low vehicular volumes (i.e., four vehicles or less per approach per cycle). Total delay is lowered in higher vehicular vol-umes (six vehicles per approach per cycle) and heavy pedestrian volumes (i.e., twenty pedestr, ans per approach per cycle) for late release pedestrian signal operations. Late release pedes. trian signal operations can produce higher right-turn capacities." Exclusive pedestrian phasing is an alterna-tive that works well to reduce turning vehicle, turn-merge multiple threat, and trapped pedestr, an acciden.. A turn-merge accident includes a vehicle that is turning and merging into a new traffic stream. A multiple threat accident involves one or more vehicles stopped m traffic and the pedestrian is his by a vehide where the driver's vision is obstructed by a stopped vehicle. A trapped vehicle accident involves a pedestrian hit at a traffic signal after he or she is trapped in the street by a traffic light change. One major study found that the use of exclusive pedestrian signals was associated with approximately a fifty percent reduction in pedestrian accidents as compared to signalized intersections with concurrent signal timing or with no pedestrian signals.. It should be mentioned, however, that scramble pedestrian phasing operates well only in very special situations. This operation works best in a situation of high pedestrian volume (Le., 1,200 or more pedestrians per day), long right turn queuing resulting from conflicts, low through volumes, and narrow streets. Streets with .dths greater than sixty feet increase the length of the scramble phase such that it becomes marginally effective. If driver violations are high, then scramble phasing can be danger-ous. Good compliance produces safer results for scramble phasing over conventional phasing; however, pedestrian and motorist delay is always higher than the signal timing options and is rarely practical to install. Care should be exercised when using scramble pedestrian phasing. Since the diagonal pedestrian movement across the intersection is permitted, the walking distance and resultant pedestrian clearance times are much longer than normal. In addition, the sight distance of the pedestrian indications is obstruct-ed by the visors for the diagonal pedestrian move- ments. A recommended methodology to assist selecting pedestrian signal phasing is given in figure 5-7 based on research conducted for Ft-IINA by Abrams and Smith.' The use of continuous through lanes at "1— intersections is not recommended. Their use requires the prohibition of pedestrian movements that would cross the continuous through lane. It is not reasonable to assume that pedestrians will comply with that prohibition. The 11oe of an actu-ated pedestrian phase for what is normally the prohibited movement at a "T" intersection has been found to be an acceptable solution in some cases. The vehicular through movement that would normally have been a simple continuous green becomes a three-section signal that is con-tinuously green, except when the pedestrian movement is actuated.
Considerations for Persons with Disabilities
Senior citizens and people with disabilities often have limited stamina and mobility. The placement of push-buttons In Inaccessible locations disco.- ages their use and creates noncompliance. If it is not practical or possible to locate the pedestrian push-button next to the sidewalk, then an apron should be installed around the pole or cabinet supporting the pedestrian push-buttons. The presence of blind and visually impaired pedestrians crossing at intersections presents unique design problems for the engi-neer. The conventional method of crossing a street is mainly predicated on the pedestrian's sense of sight. Blind and visually impaired pedes-trians have to identify the direction cars are tray eling and the approach they are on primarily by sound and touch. Blind and visually impaired people are taught to determine the direction cars are traveling, either parallel or perpendicu-lar to their Intended path, by hearing. They determine by touch with a cane where the edge of the street is located and to sense slight slopes in roadway crowns, sidewalks, or ramps. They can also detect, by subtle clues, where they are. For example, blind and visually impaired pedes-trians are taught to feel Our debris in the gutter as an indicator for the edge of the road.