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Accessible Pedestrian Signals: A Guide to Best Practices (Workshop Edition 2010) (2011)

Chapter: Chapter 3 - Understanding Traffic Signals and Modern Intersection Design

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Suggested Citation:"Chapter 3 - Understanding Traffic Signals and Modern Intersection Design ." National Academies of Sciences, Engineering, and Medicine. 2011. Accessible Pedestrian Signals: A Guide to Best Practices (Workshop Edition 2010). Washington, DC: The National Academies Press. doi: 10.17226/22902.
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Suggested Citation:"Chapter 3 - Understanding Traffic Signals and Modern Intersection Design ." National Academies of Sciences, Engineering, and Medicine. 2011. Accessible Pedestrian Signals: A Guide to Best Practices (Workshop Edition 2010). Washington, DC: The National Academies Press. doi: 10.17226/22902.
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Suggested Citation:"Chapter 3 - Understanding Traffic Signals and Modern Intersection Design ." National Academies of Sciences, Engineering, and Medicine. 2011. Accessible Pedestrian Signals: A Guide to Best Practices (Workshop Edition 2010). Washington, DC: The National Academies Press. doi: 10.17226/22902.
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Suggested Citation:"Chapter 3 - Understanding Traffic Signals and Modern Intersection Design ." National Academies of Sciences, Engineering, and Medicine. 2011. Accessible Pedestrian Signals: A Guide to Best Practices (Workshop Edition 2010). Washington, DC: The National Academies Press. doi: 10.17226/22902.
×
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Suggested Citation:"Chapter 3 - Understanding Traffic Signals and Modern Intersection Design ." National Academies of Sciences, Engineering, and Medicine. 2011. Accessible Pedestrian Signals: A Guide to Best Practices (Workshop Edition 2010). Washington, DC: The National Academies Press. doi: 10.17226/22902.
×
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Suggested Citation:"Chapter 3 - Understanding Traffic Signals and Modern Intersection Design ." National Academies of Sciences, Engineering, and Medicine. 2011. Accessible Pedestrian Signals: A Guide to Best Practices (Workshop Edition 2010). Washington, DC: The National Academies Press. doi: 10.17226/22902.
×
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Suggested Citation:"Chapter 3 - Understanding Traffic Signals and Modern Intersection Design ." National Academies of Sciences, Engineering, and Medicine. 2011. Accessible Pedestrian Signals: A Guide to Best Practices (Workshop Edition 2010). Washington, DC: The National Academies Press. doi: 10.17226/22902.
×
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Suggested Citation:"Chapter 3 - Understanding Traffic Signals and Modern Intersection Design ." National Academies of Sciences, Engineering, and Medicine. 2011. Accessible Pedestrian Signals: A Guide to Best Practices (Workshop Edition 2010). Washington, DC: The National Academies Press. doi: 10.17226/22902.
×
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Suggested Citation:"Chapter 3 - Understanding Traffic Signals and Modern Intersection Design ." National Academies of Sciences, Engineering, and Medicine. 2011. Accessible Pedestrian Signals: A Guide to Best Practices (Workshop Edition 2010). Washington, DC: The National Academies Press. doi: 10.17226/22902.
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Suggested Citation:"Chapter 3 - Understanding Traffic Signals and Modern Intersection Design ." National Academies of Sciences, Engineering, and Medicine. 2011. Accessible Pedestrian Signals: A Guide to Best Practices (Workshop Edition 2010). Washington, DC: The National Academies Press. doi: 10.17226/22902.
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Suggested Citation:"Chapter 3 - Understanding Traffic Signals and Modern Intersection Design ." National Academies of Sciences, Engineering, and Medicine. 2011. Accessible Pedestrian Signals: A Guide to Best Practices (Workshop Edition 2010). Washington, DC: The National Academies Press. doi: 10.17226/22902.
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Suggested Citation:"Chapter 3 - Understanding Traffic Signals and Modern Intersection Design ." National Academies of Sciences, Engineering, and Medicine. 2011. Accessible Pedestrian Signals: A Guide to Best Practices (Workshop Edition 2010). Washington, DC: The National Academies Press. doi: 10.17226/22902.
×
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Suggested Citation:"Chapter 3 - Understanding Traffic Signals and Modern Intersection Design ." National Academies of Sciences, Engineering, and Medicine. 2011. Accessible Pedestrian Signals: A Guide to Best Practices (Workshop Edition 2010). Washington, DC: The National Academies Press. doi: 10.17226/22902.
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Suggested Citation:"Chapter 3 - Understanding Traffic Signals and Modern Intersection Design ." National Academies of Sciences, Engineering, and Medicine. 2011. Accessible Pedestrian Signals: A Guide to Best Practices (Workshop Edition 2010). Washington, DC: The National Academies Press. doi: 10.17226/22902.
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Suggested Citation:"Chapter 3 - Understanding Traffic Signals and Modern Intersection Design ." National Academies of Sciences, Engineering, and Medicine. 2011. Accessible Pedestrian Signals: A Guide to Best Practices (Workshop Edition 2010). Washington, DC: The National Academies Press. doi: 10.17226/22902.
×
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Suggested Citation:"Chapter 3 - Understanding Traffic Signals and Modern Intersection Design ." National Academies of Sciences, Engineering, and Medicine. 2011. Accessible Pedestrian Signals: A Guide to Best Practices (Workshop Edition 2010). Washington, DC: The National Academies Press. doi: 10.17226/22902.
×
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Suggested Citation:"Chapter 3 - Understanding Traffic Signals and Modern Intersection Design ." National Academies of Sciences, Engineering, and Medicine. 2011. Accessible Pedestrian Signals: A Guide to Best Practices (Workshop Edition 2010). Washington, DC: The National Academies Press. doi: 10.17226/22902.
×
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Suggested Citation:"Chapter 3 - Understanding Traffic Signals and Modern Intersection Design ." National Academies of Sciences, Engineering, and Medicine. 2011. Accessible Pedestrian Signals: A Guide to Best Practices (Workshop Edition 2010). Washington, DC: The National Academies Press. doi: 10.17226/22902.
×
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Suggested Citation:"Chapter 3 - Understanding Traffic Signals and Modern Intersection Design ." National Academies of Sciences, Engineering, and Medicine. 2011. Accessible Pedestrian Signals: A Guide to Best Practices (Workshop Edition 2010). Washington, DC: The National Academies Press. doi: 10.17226/22902.
×
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Suggested Citation:"Chapter 3 - Understanding Traffic Signals and Modern Intersection Design ." National Academies of Sciences, Engineering, and Medicine. 2011. Accessible Pedestrian Signals: A Guide to Best Practices (Workshop Edition 2010). Washington, DC: The National Academies Press. doi: 10.17226/22902.
×
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Suggested Citation:"Chapter 3 - Understanding Traffic Signals and Modern Intersection Design ." National Academies of Sciences, Engineering, and Medicine. 2011. Accessible Pedestrian Signals: A Guide to Best Practices (Workshop Edition 2010). Washington, DC: The National Academies Press. doi: 10.17226/22902.
×
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Suggested Citation:"Chapter 3 - Understanding Traffic Signals and Modern Intersection Design ." National Academies of Sciences, Engineering, and Medicine. 2011. Accessible Pedestrian Signals: A Guide to Best Practices (Workshop Edition 2010). Washington, DC: The National Academies Press. doi: 10.17226/22902.
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Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

Accessible Pedestrian Signals: A Guide to Best Practice 25 Chapter 3: Understanding Traffi c Signals and Modern Intersection Design CHAPTER SUMMARY Th is chapter provides a description of the terminology and characteristics of traffi c signals and intersection design. It is intended to educate Orientation and Mobility (O&M) Specialists who must interact with the travel environment and traffi c engineers but who may not be familiar with all the terminology and design techniques. CHAPTER CONTENTS Introduction 26 MUTCD Warrants and Signalization 26 Intersection Signalization and Timing Plans 30 Vehicular Signals and Timing 36 Pedestrian Signals and Timing 39 Collaboration 43

26 Chapter 3: Understanding Traffi c Signals and Modern Intersection Design Introduction Intersections and signals have become more complex and it is important that Orientation and Mobility (O&M) Specialists and blind travelers understand these changes for safe travel. Skills and strategies used by pedestrians who are blind or visually impaired to cross streets at signalized intersections were developed at intersections that had pretimed signals, which meant the signal changed on a regular basis. Signalization has also become more complex, with the introduction of vehicular and pedestrian actuation and multiple phases. Th is increased complexity has made some previously accessible intersections now inaccessible for pedestrians with visual impairments. It is essential for O&M Specialists to understand these changes so that they are incorporated into their curriculum and so that these specialists can adapt their instructional techniques and advocate for their consumers’ needs. Th is chapter gives an overview of the decisions, design, and terms that are used by traffi c engineers as they design and install traffi c signals. MUTCD Warrants and Signalization WHAT IS A SIGNAL WARRANT? A warrant is a condition that an intersection must meet to justify a signal installation. Th e Manual on Uniform Traffi c Control Devices (MUTCD) specifi es eight ”traffi c control signal needs studies”, known as warrants. However, “Th e satisfaction of a traffi c signal warrant or warrants shall not in itself require the installation of a traffi c control signal.” (MUTCD, 4C.01) Th e fi nal decision is made based upon the traffi c engineer’s judgment. PROCESS TO DETERMINE IF SIGNAL IS WARRANTED Th e traffi c engineer analyzes vehicle traffi c volume, pedestrian activity, intersection crash history, and the physical environment in order to determine whether or not the intersection warrants a traffi c control signal. Engineers examining the intersection may review the following: • Number of vehicles entering the intersection from all directions during 4-hour and 8-hour periods • Vehicular volumes during peak hours, classifi ed by vehicle type for traffi c movement in all directions • Pedestrian volume on each crosswalk in all directions, including children, the elderly, and/or persons with disabilities, during each hour of the day

Accessible Pedestrian Signals: A Guide to Best Practice 27 • Requests from participants attending nearby facilities and activity centers that serve the young, elderly, and/or persons with disabilities • Posted speed limit • Physical layout • Crash experience/history Diff erent warrants require detailed analysis of diff erent aspects of the above information. EXAMPLES OF SIGNAL WARRANTS Information on two of the signal warrants is included below to illustrate some of the considerations. Warrant 1 — Eight- Hour Vehicular Volume Engineers evaluate the vehicles per hour and a certain volume must be met in order to justify installation. A complex table is used that includes the number of lanes of moving traffi c for each approach, vehicles per hour on the major street, and vehicles per hour on the higher volume minor street approaches. Standard (MUTCD, Section 4C.02): Th e need for a traffi c control signal shall be considered if an engineering study fi nds that one of the following conditions exist for each of any 8 hours of an average day (See Table 3-1): • Th e vehicles per hour given in both of the 100 percent columns of Condition A in Table 3-1 exist on the major-street and the higher-volume minor-street approaches, respectively, to the intersection; or • Th e vehicles per hour given in both of the 100 percent columns of Condition B in Table 3-1 exist on the major-street and the higher-volume minor-street approaches, respectively, to the intersection. In applying each condition the major-street and minor-street volumes shall be for the same 8 hours. On the minor street, the higher volume shall not be required to be on the same approach during each of these 8 hours. Option: If the posted or statutory speed limit or the 85th-percentile speed on the major street exceeds 70 km/h (40 mph), or if the intersection lies within the built-up area of an isolated community having a population of less than 10,000, the traffi c volumes in the 70 percent columns in Table 3-1 may be used in place of the 100 percent columns.

28 Chapter 3: Understanding Traffi c Signals and Modern Intersection Design a Basic minimum hourly volume. b Used for combination of Conditions A and B after adequate trial of other remedial measures. c May be used when the major-street speed exceeds 70 km/h (40 mph) or in an isolated community with a population of less than Warrant 4 — Pedestrian Volume Engineers evaluate the level of pedestrian activity at an intersection to see if a signal is warranted. Th e MUTCD describes Warrant 4 as “Th e Pedestrian Volume signal warrant is intended for application where the traffi c volume on a major street is so heavy that pedestrians experience excessive delay in crossing the major street.” (MUTCD, 4C.05) As currently written, the warrant requires a fairly large volume of pedestrians crossing at a location. “Th e need for a traffi c control signal at an intersection or mid-block crossing shall be considered if an engineering study fi nds that both of the following criteria are met: Table 1. Applicable Variables for Mid-Block Crossings CONDITION A —MINIMUM VEHICULAR VOLUME Number of lanes for moving traffi c on each approach Vehicles per hour on major street (total of both approaches) Vehicles per hour on higher-volume minor- street approaches (one direction only) Major Street Minor Street 100% a 80%b 70%c 100%a 80%b 70%c 1 1 500 400 350 150 120 105 2 or more 1 600 480 420 150 120 105 2 or more 2 or more 600 480 420 200 160 140 1 2 or more 500 400 350 200 160 140 CONDITION B—INTERRUPTION OF CONTINUOUS TRAFFIC Number of lanes for moving traffi c on each approach Vehicles per hour on major street (total of both approaches) Vehicles per hour on higher-volume minor- street approaches (one direction only) Major Street Minor Street 100% a 80%b 70%c 100%a 80%b 70%c 1 1 750 600 525 75 60 53 2 or more 1 900 720 630 75 60 53 2 or more 2 or more 900 720 630 100 80 70 1 2 or more 750 600 525 100 80 70

Accessible Pedestrian Signals: A Guide to Best Practice 29 • Th e pedestrian volume crossing the major street at an intersection or mid-block location during an average day is 100 or more for each of any 4 hours or 190 or more during any 1 hour; and • Th ere are fewer than 60 gaps per hour in the traffi c stream of adequate length to allow pedestrians to cross during the same period when the pedestrian volume criterion is satisfi ed. Where there is a divided street having a median of suffi cient width for pedestrians to wait, the requirement applies separately to each direction of vehicular traffi c.” (MUTCD, 4C.05) In addition: • “Th e Pedestrian Volume signal warrant shall not be applied at locations where the distance to the nearest traffi c control signal along the major street is less than 90 m (300 ft), unless the proposed traffi c control signal will not restrict the progressive movement of traffi c.” (MUTCD, 4C.05) However: • “Th e criterion for the pedestrian volume crossing the major roadway may be reduced as much as 50 percent if the average crossing speed of pedestrians is less than 1.2 m/sec (4 ft/sec).” (MUTCD, 4C.05) FOR MORE INFORMATION Th e current MUTCD can be downloaded from the following website: http://mutcd.fhwa.dot.gov/

30 Chapter 3: Understanding Traffi c Signals and Modern Intersection Design Intersection Signalization and Timing Plans INTERSECTION SIGNALIZATION Intersections are generally designed to provide optimal vehicle traffi c fl ow. Timing plans may be of two general types: • fi xed time (or pretimed) • actuated A signal at a given intersection may be designed to change from actuated to pretimed to fl ashing mode depending upon: • time of day (peak periods vs. non-peak periods); • day of week; and • malfunctions due to power outages. It is important for O&M Specialists to understand the signal design and terminology to teach these concepts to their students. Th ere is some variability in timing plans in diff erent municipalities and in diff erent locations, depending on the roadway needs and local practices. SIGNAL DESIGN TERMS Phase — the right-of-way, yellow change, and red clearance intervals in a cycle that are assigned to an independent traffi c movement or combination of movements Interval — the part of a signal cycle during which signal indications do not change • In other words, a phase is the time allotted to a specifi c movement, such as northbound traffi c, whereas an interval is how long the light stays green, yellow, or red for vehicles or WALK, fl ashing DONT WALK, or DONT WALK for pedestrians. • Busier intersections typically have separate phases for left turn movements (i.e., protected left turns). When a major road intersects a minor road, the green intervals for the major road will be longer than those for the minor road to accommodate the heavier traffi c on the major road. • Although the MUTCD gives specifi c defi nitions to “phase” and “interval”, these terms are often used interchangeably by traffi c engineers. Cycle — sum total of all phases at a signal • A cycle is timed from the start of one phase to the start of that same phase when it comes around again. • Larger, busier intersections will commonly have longer cycles.

Accessible Pedestrian Signals: A Guide to Best Practice 31 PRETIMED (FIXED TIME) SIGNALS Pretimed intersections operate in predetermined and predictable fashion. • Regularly repeated sequence of phases (often 30 seconds or more), regardless of traffi c fl ow • Length of phases may change at diff erent times of day, based on a consistent timing plan, for example, one street may have longer phases at peak hours than non-peak hours • Still found in many locations, particularly in downtown areas ACTUATED SIGNALS Actuated signals change the length and/ or order of the phases in response to variations in vehicle or pedestrian traffi c. • Detectors monitor traffi c and send signals to the traffi c signal controller. Detectors are most often inductive loops (electric), though they may be magnetic, microwave, video, and other detection technologies. • Pushbuttons are most often used for pedestrian detection, though other “pedestrian sensing” technologies (microwave, infrared, piezoelectric) may be used as well. • Used where traffi c volumes fl uctuate or where it is desirable to minimize interruptions to traffi c fl ow on the major street. Detectors are often placed on minor roads and in turn lanes to detect when a motorist is waiting to make a turn. • Vehicular actuation allows the cycle to skip phases, so pedestrians with visual impairments cannot accurately predict, based on previous experience, when in the cycle the pedestrian phase will begin. • Some actuated signals may provide very short phases to accommodate a single vehicle, without provision of a pedestrian phase during that cycle. A pedestrian who is blind crossing parallel to that vehicle may not realize that a pedestrian phase is not provided during that vehicle’s movement. Figure 3-1. Photograph of vehicle detector loops in pavement Figure 3-2. Photograph of vehicle detector loop in pavement

32 Chapter 3: Understanding Traffi c Signals and Modern Intersection Design Th e extent of actuation is dependent on geometric and operational requirements, but is generally categorized as either semi-actuated or fully actuated. Semi-actuated signals • Common at the intersection of a main road and a minor side street • Main roadway signal stays in green until a side street detection is received, causing the traffi c signal to change (the WALK signal for the crossing the main roadway may not come on unless pedestrian pushbutton is pressed) • Vehicle detectors only on the side street; pedestrian detectors are also possible only on the side street • Pedestrian activation (usually use of pushbutton) activates signal to give WALK interval for pedestrian phase to cross the major street • Pedestrian signal for side street crossing may “rest-in-WALK” (gives the WALK indication during the green signal for the major street) for the visual pedestrian signal with no pushbutton installed Fully actuated signals • Common at the intersection of two main roads (arterials) • All movements/ phases are actuated • Detectors for vehicles on all approach lanes • Pedestrian pushbuttons or detection to activate WALK signal for pedestrian crossings • Used when traffi c volumes on each approach vary by time of day • Used to skip phases within a cycle when vehicles are not present, thus minimizing delay • Changing traffi c volume can result in diff erence in timing and sequence of phases for every cycle BASIC TURNING PHASES Protected turn A protected turn is made without opposing through vehicular traffi c or pedestrian crossing. • Denoted for motorists by a green arrow • Typically activated by a vehicle detector • Th e signal phasing “protects” vehicles by prohibiting the opposing movements, including pedestrian movements • Protected turns require a separate signal phase, which leads to multiphase signalization (more than two phases at the intersection)Figure 3-3. Protected left turn signal

Accessible Pedestrian Signals: A Guide to Best Practice 33 Permissive turn A permissive turn is made across an opposing fl ow of through vehicles and/or pedestrians. • Typically denoted for motorists by a circular green (green ball) signal • Th e driver is “permitted” to cross the opposing through fl ow, but must select an appropriate gap in the opposing traffi c stream through which to turn • Th e driver must also yield to pedestrians who are crossing lawfully within the intersection • Th is is the most common type of left-turn phasing at signalized intersections, and is used both when left-turn volumes are not excessive and where adequate gaps of suffi cient size exist in the opposing traffi c to accommodate turns safely DESIGN OF TURNING MOVEMENTS Concurrent (dual) left turns • Two directions of turning traffi c (eastbound and westbound) proceed together as the opposing through traffi c on the same approaches is stopped (protected left turn phasing) • Can be activated either before or after the opposing through fl ows have had their green phase. If the left turn comes before the opposing through movement, it is called a “leading left turn”. If it comes after, it is called a “lagging left turn”. Leading left turns, which are much more common than lagging left turns, can create safety problems for blind pedestrians, since the surging left turn traffi c may be mistaken for the parallel through traffi c surge. Split or non-concurrent phasing • Split phasing provides separate green time to vehicles on opposing approaches • In typical signal design, the northbound and southbound through movements run simultaneously, as do the eastbound and westbound through movements. At off set intersections and locations where there are heavy turn movements, split phasing may be used to allow movements on each approach to move independently of other approaches. • Pedestrian phases for parallel crosswalks will be activated at diff erent times. Th e pedestrian phase for a crosswalk will coincide with the through traffi c movement immediately adjacent to that crosswalk. • Where there is split phase timing, the surge of parallel vehicles beside the pedestrian may be mistaken as indicating the onset of the WALK interval and blind pedestrians may cross into the paths of left turning vehicles. In addition, the heavy fl ow of turning traffi c may be mistaken for the surge of traffi c on the street beside the blind pedestrian, when the traffi c is actually on the street the pedestrian is crossing. Figure 3-4. Permissive green ball signal

34 Chapter 3: Understanding Traffi c Signals and Modern Intersection Design Example of northbound/southbound movements running under split phasing (see Figure 3-5): 1. Northbound traffi c, including traffi c turning east and west, moves on one signal phase, (southbound traffi c and all traffi c on the E/W street have a red signal at that point). Th e pedestrian phase usually is provided at this time for pedestrians on the east crosswalk 2. Northbound traffi c receives a red light while all southbound traffi c, including turning traffi c, is allowed to go. Th e pedestrian phase usually provided at this time is for pedestrians crossing on the west crosswalk FLASHING OPERATION Signals may only operate during peak periods of the day and may switch to fl ashing operation at non-peak hours, late at night, or in response to a signal malfunction. • Signals no longer operate under stop-and-go sequencing • Signals usually fl ash red for side streets and fl ash yellow for the main street or fl ash red for both streets • Pedestrian signal heads (WALK/DONT WALK signs) are dark and APS are silent COORDINATED SYSTEMS Coordinated systems provide automated control of signal timing to two or more signalized intersections. Instead of looking at an intersection in isolation, coordinated systems look at an entire arterial or network of intersections and make signal timing adjustments that Figure 3-5. Illustration of split phasing

Accessible Pedestrian Signals: A Guide to Best Practice 35 benefi t (optimize) the operation of the entire system. System changes are a result of traffi c volume and travel times. Most often, a central controller (computer) provides the primary control and communicates with individual controllers located at each intersection. Coordinated control has a number of advantages from a vehicle perspective: • Signals can be controlled from a central traffi c management center • Th e detection elements of the system can be used to predict future fl ows within the network and adjust the signal timing proactively instead of reactively Signals in a coordinated system can present problems for blind pedestrians: • Th e green time given for vehicles on the intersecting road (not the road whose signals are coordinated) may be less than normal to fi t into the timing scheme of the coordination • Th is shorter time can be insuffi cient for pedestrians to cross the major road. Pedestrian who are blind will not know that there is insuffi cient time and may directly confl ict with the approaching platoon of traffi c on the major road. Th is demonstrates a need for APS at the intersection.

36 Chapter 3: Understanding Traffi c Signals and Modern Intersection Design Vehicular Signals and Timing MEANING OF SIGNALS Th e use of particular traffi c signal colors and symbols, and their meaning, is described in Part 4 of the MUTCD. Signs and pavement marking used at signalized intersections are covered in Parts 2 and 3 of the MUTCD, respectively. Although this section presents basic traffi c laws concerning signals, it is important to be well educated on the specifi c laws of the state of interest. Some laws, such as right- turn-on-red-arrow, vary from state to state. Most states provide a Drivers Handbook that presents this sort of information. STEADY GREEN SIGNAL Circular green (green ball): • Traffi c, except pedestrians, may proceed straight through or turn right or left except as such prohibition signs or markings modify movement. Vehicles turning right or left shall yield the right-of-way to pedestrians lawfully within the intersection. Green Arrow: • Traffi c may make the movement indicated by the green arrow. Opposing vehicle and pedestrian movements will be given a red signal or DONT WALK indication. Pedestrian movement: • Pedestrians may cross unless a green arrow indicates confl icting traffi c will cross into their path or unless a pedestrian signal indicates otherwise STEADY YELLOW SIGNAL • Warning that the green interval has ended and the red signal will begin. Pedestrian movement: • Pedestrians do not have enough time to cross and should not initiate a crossing. STEADY RED SIGNAL • Traffi c must stop at the stop line, before the crosswalk lines, or before the intersecting street.

Accessible Pedestrian Signals: A Guide to Best Practice 37 Right turn on red: • Unless a sign or local law prohibits right turn on red, vehicles must come to a complete stop but are allowed to then proceed with the turn if a safe gap in traffi c is available. • Turning vehicles must yield right-of-way to pedestrians and traffi c already in the intersection. • Right-turn-on-red makes it harder to determine the surge of traffi c at the onset of vehicular green on the street parallel to the crossing direction. Blind travelers must wait to hear a car traveling straight across the intersection to determine that the light has changed, so they frequently are delayed in initiating crossings while they determine that parallel traffi c fl ow has begun. Left turn on red: • Th is maneuver involves a left turn from a one-way street onto another one-way street on a red signal (same procedure as stated above for right turn on red). Th is is not allowed in some states. Red arrow: • Vehicles must stop at a stop line, before the crosswalk lines, or before the intersection. Some states allow vehicles to turn right on red after stopping. Pedestrian movements: • Pedestrians should not enter the roadway in the direction of travel controlled by a steady red signal FLASHING YELLOW • Proceed with caution, treated like Yield sign FLASHING RED • Stop, then go, treated like Stop sign FLASHING RED ARROW & FLASHING YELLOW ARROW • Typically have the same meaning as fl ashing circular signal indication, except they apply only to vehicular traffi c intending to make the movement indicated by the arrow. • In some states, fl ashing circular yellow and yellow arrow indications may be used during stop-and-go traffi c signal operations for permissive left-turn indications (same control as a green ball for left turns) • In some states, fl ashing circular red and red arrow indications may be used during stop-and-go traffi c signal operations for permissive left-turn indications

38 Chapter 3: Understanding Traffi c Signals and Modern Intersection Design OTHER INTERSECTION TERMINOLOGY Channelized turn lane (slip lane) — a turn lane that channels turning drivers to a position where they will either yield to oncoming traffi c or complete a “free fl owing” turn, which means the turning vehicles have a dedicated lane on the road they are entering and therefore do not need to stop or yield to traffi c. Figure 3-6. Channelized right turn lane

Accessible Pedestrian Signals: A Guide to Best Practice 39 Pedestrian Signals and Timing VISUAL PEDESTRIAN SIGNALS Pedestrian signal heads (“pedheads”) are installed at some intersections to instruct pedestrians when it is lawful to cross. Th is is typically done where there is a signifi cant amount of pedestrian activity or for safety-based reasons, such as the possibility of confusion for pedestrians taking cues from the traffi c signal. Pedestrian signals have three intervals: • WALK interval — White WALK or symbol of a person walking issued to indicate that pedestrians should begin crossing, after yielding to vehicular traffi c still legally in the crosswalk. • Change interval — Orange fl ashing DONT WALK or symbol of a fl ashing hand is used when pedestrians are not supposed to begin a crossing because there is not enough time left in the phase for most pedestrians to get all the way across the street. Pedestrians that have already begun to cross should fi nish crossing. • DONT WALK interval — Steady orange DONT WALK or symbol of a hand is used when pedestrians are not supposed to be in crosswalk. Figure 3-7. Typical pedestrian signal symbols

40 Chapter 3: Understanding Traffi c Signals and Modern Intersection Design Some locations also use pedestrian countdown signals. Th ese signals provide the countdown in seconds for the remaining time allotted during the change interval. • Countdown signal supplements the WALK/DONT WALK signals, rather than replacing them. • MUTCD guidance stipulates that the countdown should only be displayed during the fl ashing DONT WALK interval because of inconsistencies of the countdown during WALK at actuated signals. However, many cities are still using signals that display the countdown during the WALK interval (see Figure 3-9). Pedestrians with low vision have had problems distinguishing the countdown numbers from the orange fl ashing hand symbol when they are displayed alongside the white walking-man symbol. PEDESTRIAN SIGNAL TIMING Pedestrian signal timing design deals with the length of the WALK and change intervals. Th e WALK interval is typically short (around 4 to 7 seconds). Th e change interval is designed to be long enough for a pedestrian to cross the street. Th is is typically calculated assuming a walking speed of 3.5 to 4 feet per second. Parking lanes might be excluded from the calculation. Th e green time for the parallel traffi c movement is calculated based on the time necessary for a pedestrian to cross the street (see equation below). Th e fi gure below illustrates how the vehicle and pedestrian phases overlap. Time is the horizontal axis in the picture. Th is is a typical signal timing diagram used by traffi c engineers in the design of the signal timing. Figure 3-9. Incorrect display because countdown is displayed during WALK interval Figure 3-8. Correct display of pedestrian countdown signal (counting down during fl ashing DONT WALK) Minimum Green Time = WALK interval + Crosswalk Length 4.0 ft/sec Flashing DON'T WALK Figure 3-10. Illustration of the overlay of vehicle signal and pedestrian signal timing

Accessible Pedestrian Signals: A Guide to Best Practice 41 PEDESTRIAN PHASE ACTUATION Some signals are designed so that the pedestrian phase is actuated by a pushbutton. • Pressing the pushbutton calls a pedestrian phase which allows enough time for the pedestrian to cross at average walking pace • Without pushing the button, there may not be enough time programmed into the vehicular phase for a pedestrian to cross the street. If the button is pressed, the pedestrian phase may begin immediately or will begin at a certain point during the following cycle. • Extent of the delay before it begins will vary depending on the programming of the phases for that intersection and when the button was pushed within the cycle. • Blind pedestrians have traditionally waited through a light cycle to assess and refi ne their heading by listening to vehicular trajectories, before crossing on the next pedestrian phase. At a pedestrian-actuated intersection, that is not possible because pedestrians have to cross on the next pedestrian phase after pushing the button. If they do not cross at that time, it is necessary to locate and push the button again (and re-establish their alignment). PASSIVE PEDESTRIAN DETECTION • Pedestrians may be detected passively (without pushing a button) as they approach the crosswalk area through the use of microwave, infrared or piezoelectric technologies. • Future developments may impact whether or not an APS with a locator tone is necessary at an intersection that uses passive detection. One issue for consideration is that pedestrians may not realize they have been detected. LEADING PEDESTRIAN INTERVALS • Provides a pedestrian WALK interval 2 to 4 seconds before the vehicular green, allowing pedestrians a head start so they are in the intersection before vehicles start up. • However, this can be a disadvantage to pedestrians who are blind or visually impaired who rely on the surge of traffi c to recognize when the signal is green. If these pedestrians begin crossing with the surge of parallel traffi c where a leading pedestrian interval is used, they will have less time to cross than was designed. Also, when pedestrians do not initiate their crossing at the onset of the WALK interval, drivers may interpret this to mean that the pedestrians are not intending to cross. • Pedestrians who are blind or visually impaired do not know about the leading pedestrian interval at unfamiliar intersections unless there is an APS installed.

42 Chapter 3: Understanding Traffi c Signals and Modern Intersection Design EXCLUSIVE PEDESTRIAN PHASING • All vehicles have a red light during the WALK interval and all crosswalks have the WALK signal at the same time. • Typically done to increase pedestrian safety. At some locations, right-turn-on- red is allowed during the pedestrian phase. • Crossings may be made diagonally for pedestrian effi ciency. • Exclusive pedestrian phasing may be followed by an extended time for one or more of the crosswalks. • Exclusive pedestrian phasing may be benefi cial to pedestrians with mobility impairments and cognitive disabilities as it allows time to cross when no or few vehicles are moving through the intersection. However, it is a disadvantage for pedestrians who rely on traffi c sounds to determine the signal phases. In addition, initial alignment and maintaining alignment during crossings may be diffi cult due to the absence of parallel moving traffi c. PED RECALL • WALK indication will be given every cycle (as if someone were always there pushing the button). REST-IN-WALK • Pedestrian signal to cross the minor street remains in WALK as long as the major street has green, and there is no call on the minor street • When a vehicle approaches on minor street and is detected, the pedestrian signal to cross the minor street changes to fl ashing DONT WALK • APS during Rest-in-WALK: instead of sounding constantly, some APS manufacturers provide a limit switch that limits the length of the audible WALK indication to seven or eight seconds, but recalls the audible and vibrotactile indications of the WALK if the button is pressed when there is adequate clearance time remaining.

Accessible Pedestrian Signals: A Guide to Best Practice 43 Collaboration CONTACTING LOCAL TRANSPORTATION PROFESSIONALS Transportation professionals may consist of traffi c engineers, public works personnel, signal technicians, and/or transportation planners. In some cases, local consulting engineering fi rms are contracted to provide operation and maintenance control of signalized intersections. Th e ownership of the signal, whether it is at the township, county, city or state level, designates which transportation professional would be in charge of the intersection. Make contact with the transportation professional by contacting your local government offi ce. Work in a collaborative manner and develop a productive working relationship: • Talk with the transportation professional and familiarize yourself with the procedures to accommodate your request. • Understand that additional parties and factors may be involved when addressing your request (funding, politics, etc). • Ask transportation professionals about signal phasing and timing plans at particular intersections and how pedestrians are accommodated. UNDERSTAND MUNICIPALITY STRUCTURE Structure varies from one municipality to the next: • Engineering may be part of public works, or it may be a separate department • Intersection signals may be part of a state or county traffi c management network, even if within a town or city, or they may be managed by a consulting fi rm • New construction of an intersection may be contracted out to a traffi c engineering or electrical contractor • Signals may be maintained by a diff erent department than the one that installed them • Learn if there is a local jurisdiction or statewide ADA coordinator and/or a Department of Transportation/Public Works Department ADA coordinator. Th is coordinator may ensure that the local jurisdiction’s streets, sidewalks and facilities are accessible to pedestrians with disabilities. Th e coordinator may also have more infl uence in getting traffi c engineers to install accessible signals than someone outside of the local jurisdiction. To learn about a city department structure, check the city web site or check a phone directory for offi ces and structure information.

44 Chapter 3: Understanding Traffi c Signals and Modern Intersection Design CONTACT PERSON IN TRAFFIC ENGINEERING DEPARTMENT Call the department that manages traffi c signals and ask who to talk to about a specifi c intersection. • Call and explain to the transportation professional what you do and why you want to know about the intersection (people responsible for the traffi c signals may not have considered all travel strategies and may not know that professionals exist to consult with about the travel needs of pedestrians with visual impairments) • Ask the person in charge for more information about who does what and how to ask for information • Find out the procedure for requesting changes or modifi cations to an intersection ATTEND MEETINGS Consider attending: • Local pedestrian advisory/advocacy meetings. Many towns set up these groups to solicit feedback on pedestrian issues and advice on potential solutions. • Local meetings of the Institute of Transportation Engineers (ITE) or other engineering professional meetings. • Local Disability Advisory Committee meetings. Th e Disability Advisory Committee reports directly to elected offi cials (Mayor, City Council, and County Board of Supervisors) of the local jurisdiction. If the Disability Advisory Committee has a Physical Access Subcommittee, an O&M specialist may want to become a permanent member in order to have an opportunity to advocate for and infl uence future installations of accessible signals. PUBLIC HEARINGS Consider attending Transportation Improvement Plan (TIP) public hearings: • Opportunities provided to meet Department of Transportation staff and/or traffi c engineers. • Present brief comments on the needs of pedestrians. EDUCATE YOURSELF Keep informed: • Familiarize yourself with APS installations in your area or nearby areas • Learn the language used by traffi c engineers • Familiarize yourself with state regulations and practices such as MUTCD, ADA Title II and Draft PROWAG

Accessible Pedestrian Signals: A Guide to Best Practice 45 • Learn the desires of others in your community • Remain informed on current APS technology • Follow up on any requests and do not assume someone else is doing everything right • Learn where to report problems or malfunctions EDUCATE YOUR STUDENTS Responsibilities to students: • Teach students about changes in signalization and intersection geometry • Explain the necessity of using pushbuttons at actuated intersections • Remind students that timing plans can vary, so the signal timing they identify when crossing the intersection at a specifi c time of day or day of week may be diff erent the next time they use the same intersection • Assist students in requesting an APS • Teach students how to use APS ADVOCATE FOR APS Advocate for APS, especially at intersections when: • Pedestrians are unable to discern the WALK interval • A pedestrian pushbutton controls the pedestrian crossing phase • Signalization includes a leading pedestrian interval or an exclusive pedestrian phasing • Many electric or hybrid vehicles are present

46 Chapter 3: Understanding Traffi c Signals and Modern Intersection Design

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TRB’s National Cooperative Highway Research Program (NCHRP) Web-Only Document 150: Accessible Pedestrian Signals: A Guide to Best Practices (Workshop Edition 2010) provides an introduction to accessible pedestrian signals (APS) and highlights issues related to the design, installation, operation, and maintenance of APS.

The report also addresses public education, U.S. case studies, and international practice related to APS. In addition, the report explores issues related to travel by pedestrians who are blind or who have low vision, and examines traffic signals and modern intersection design.

NCHRP Web-Only Document 150 is designed to serve as a companion resource document to a one-day training course on accessible pedestrian signals. For information on the training program, contact Stephan Parker of TRB at SAParker@nas.edu.

NCHRP Web-Only Document 150 is a reformatted edition of and replaces NCHRP Web-Only Document 117A: Accessible Pedestrian Signals: A Guide to Best Practice.

On July 20, 2011, TRB co-sponsored a web briefing or "webinar" that explored information about the project. As a part of the webinar, panelists provided information about how to host a free APS workshop offered through NCHRP. Details about the webinar can be found on our website.

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