Infrastructure Design Directive (IDD-2011-05) 13 September 2011 Page 2 DISTRIBUTION LIST Paul Gray Kathy Bender Ernest Archuleta Max Valerio Muffet Cuddy NORTH REGIONAL DESIGN DIVISION David Quintana Antonio Valdez Mike Kirby Daniel Maes Johnny Herrera Ricardo Roybal Carlos Ruiz CENTRAL REGIONAL DESIGN DIVISION Keun-Wook Yi Mark Fahey Rais Rizvi Carlos Castaneda Steve Lopez Paul Lindberg Greg Clarke Hooshang Tavanaiepour Osvaldo Reyes-Alicea SOUTH REGIONAL DESIGN DIVISION Gabriela Contreras-Apodaca Michael Smelker/Vince Pena Sherri Holliefield/Michael Hernandez Arthur Romero/Jesus Chavarria Tisha Clark/Refugio Perea ENGINEERING SUPPORT DIVISION Jeff Mann BRIDGE BUREAU Ray Trujillo Zann Jones Tim Marrs/Sherman Peterson Jeff Johnston/Jeff Vigil Thomas Cartner DRAINAGE BUREAU Ted Barber Reza Afaghpour/Timothy Trujillo Ellery Biathrow/Hashem Faidi David Trujillo Jr/Morris Muskett

TRAFFIC TECHNICAL SUPPORT BUREAU Afshin Jian Brad Julian Richard Allison PROGRAM MANAGEMENT DIVISION Elias Archuleta PROJECT PRODUCTION & SCHEDULING BUREAU Phillip Montoya Victoria Cruz P. S. & E. BUREAU Ron Trujillo Jeff Martinez Daniel Bustamante/Dean Serna/Bob Bachicha Christine Griego/Sally Gomez/Jeri Romero Norbert Baca/James Mexia QUALITY ASSURANCE UNIT Yolanda Roybal Pablo A. Garcia STATE CONSTRUCTION BUREAU David E. Trujillo Steve Hemphill Ken Cordova Armando Armendariz Rick Padilla STATE MAINTENANCE BUREAU Dennis Ortiz ENVIRONMENTAL DESIGN DIVISION Blake Roxlau Jeffery Fredine William Hutchinson ENVIRONMENTAL GEOLOGY BUREAU Audrey Moore OFFICE OF PROPERTY ASSET MANAGEMENT Clyde Archibeque PLANNING DIVISION Patricia Oliver-Wright Anne McLaughlin Titus Ispirescu

Infrastructure Design Directive (IDD-2011-05) 13 September 2011 Page 3 SURVEY & LANDS DIVISION Rob Sexton ROW/UTILITIES DIVISION Ron Noedel DISTRICT ENGINEERS 1/Frank Guzman 2/Gary Shubert 3/Tammy Haas 4/Jimmy Camp 5/Miguel Gabaldon 6/Larry Maynard ASSISTANT DISTRICT ENGINEERS 1/Filiberto Castorena/Harold Love 2Ralph Meeks/Ismael Dominguez 3/Ken Murphy/Kathy Trujillo 4/Abel Esquibel 5/James Gallegos 6/Fernando Trujillo/Lisa Vega ENGINEERING SUPPORT 1/Harold Love 2/Robert Kurtz 3/Tony Abbo 4/Heather Sandoval 5/Phil Gallegos 6/Ron Romero DISTRICT TECH SUPPORT ENGINEERS 1/Harold Love 2/Louis Matta 3/Priscilla Benavides 4/Mohamad Assaad/Leon Ortega 5/David Martinez 6/Bryan Peters DISTRICT TRAFFIC ENGINEERS 1/Maria Hinojos 2/Earle Smith 3/Antonio Jaramillo 4/Adam Romero 5/Ruben Garcia 6/Jeffrey Sanchez STATE MATERIALS BUREAU Robert McCoy Bob Meyers Parveez Anwar

FHWA Frank Lozano Steven Von Stein Thiet Nguyen Rodolfo Monge-Oviedo Robert Bency Viven Hoang Monica Jurado Jolena Palau ACTIVE CONSULTANTS Charlie Trujillo, AECOM Eric Hawton, AMEC Pierce Runnels, ASCG, Inc. Albert Thomas, Bohannan-Huston, Inc. Ross Lujan, CH2MHILL Steven Vasquez, Chavez-Grieves Dave Maxwell, Engineers Inc. David Wilson, Gannett-Fleming West, Inc. Peter Brakenhoff, HDR Engineering Inc. Kim Kemper, Huitt Zollars, Inc. Lawrence Ortega, Lawrence Ortega Ivan Trujillo, Louis Berger Group Kent Freier, Molzen-Corbin & Associates (Albuquerque) John Montoya, Molzen-Corbin & Assoc. (Las Cruces) Joann English, North Sound Consulting, Inc. Clay Koontz, OCCAM Consulting Engineers, Inc. Hal Byrd, Parsons Brinckerhoff Quade & Douglas Fernando Quiroga, Quiroga-Pfeiffer Engr.Corp. Carlos Padilla, Radian Engineering Joseph Chato, REM-Santa Fe Engineering LLC Steven Harris, Renaissance Engineering LLC Elvidio Diniz, Resource Technology Robert Smith, Smith Engineering Co. (Albuquerque) Jim Landfair, Smith Engineering Co. (Roswell) Jim Smith, Souder Miller & Associates Lester Cisneros, Tampa Bay Engineering John Andrews, The Larkin Group Jim Witkowski, TransCore ITS, Inc. Peter Hinckley, URS Greiner Woodward Clyde Chris Baca, Vector Engineering William Ventry, Ventry Engineering Scott Perkins, Wilson & Company

Infrastructure Design Directive (IDD-2011-05) 13 September 2011 Page 4 METROPOLITAN/REGIONAL PLANNING Jack Lord, MRCOG Loretta Tollefson, MRRPO Joe Delmagori, FMPO Andy Hume, LCMPO Keith Wilson, SFMPO Michael Medina, EPMPO Renee Ortiz, EPCOG Lesah Sedillo, NERPO Bob Kuipers, NWRPO Tony MacRoberts, SCRPO Mary Ann Burr, SERPO Sandy Chancey, EPRPO Cynthia Stoehner, SWRPO ACONM Mike Gibson

Traffic Signal Yellow Change, Red Clearance, Pedestrian Clearance Policy and Dilemma Zone Guidance 

 This document provides the New Mexico Department of Transportation a consistent policy for the deployment  of  traffic  signals  change  intervals  and  dilemma  zone  protection  options  for  use throughout the State of New Mexico. Engineering  judgment should be applied to the special cases and  situations  for which guidance provided here  could not be  readily applied.  In  these  cases, an engineering  investigation  should be done and  the methodology should be approved by a NMDOT Traffic Technical Support Engineer.  Yellow Change Interval  The  recommended  yellow  change  interval  for  traffic  signals  maintained  by  the  New  Mexico Department of Transportation (NMDOT) and traffic signals  located within NMDOT  jurisdiction shall be based on the posted speed for the approaching vehicles, driver’s reaction time, and intersection vertical geometry.     The yellow change interval is calculated by the following formula:   

 

 where:        y = length of yellow change interval (seconds) 

 t = Driver perception/reaction time (typical 1.0 second)         v = posted speed for approaching vehicle (miles per hour)         a = deceleration rate (typical 10 ft/sec2)         g = acceleration due to gravity (32.2 ft/sec2)         G = grade of approach (percent, %)  Table 1  (page 7) presents  the  recommended  values of  yellow  change  interval  for  various posted speed  values  and  downgrades  less  than  1%.  The minimum  yellow  change  interval  shall  be  3.0 seconds  and  the maximum  shall  be  5.0  seconds.  Yellow  change  interval  should  be  adjusted  for intersection approach downgrades greater than 1% but not for upgrade approaches. When yellow change  intervals are calculated to be  larger than 5.0 seconds the excess time may be added to the red clearance interval. All calculations are rounded up to nearest 0.5 seconds.  When applying the above equation to determine yellow change interval for left‐turn phases, the ITE Traffic  Signal Timing Manual  recommends  that  the  speed used  should  reflect  that of  the  turning drivers rather  than posted speed. This speed could equal  that of  the adjacent  through movement but  it can also be slower as  left‐turn drivers  inherently slow to a comfortable turning speed. With this  in mind, the recommended yellow change  interval  for a  left‐turn phase  is 3 seconds.    If  the left‐turn phase terminates concurrently with the adjacent through phase, for instance in lagging left‐turn phase,  the yellow change duration should correspond  the  through yellow phase because  the phases are interlocked by the ring‐barrier operation. 

 

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Red Clearance Interval  The  recommended  red clearance  interval shall be based on  the width of  the  intersection and  the posted speed of the approach.   The red clearance interval is calculated by the following formula:  

2

 where:        r = length of red clearance interval (seconds) 

W = width of intersection (feet) L = Length of vehicle (typical 20 feet) 

        v = posted speed of approach (miles per hour)          The width of the intersection (W) (see Figure 1) should be measured from the near‐side stop line to the far edge of the last conflicting traffic lane along the subject vehicle travel path. If crosswalks and heavy  pedestrian  volumes  are  present  at  the  intersection,  width  of  the  intersection  may  be measured from the near‐side stop line to the far side of the pedestrian crosswalk on the far side of the intersection (W alt in Figure 1).  

Figure 1.  Width of Intersection Variable for Red Clearance Calculation  

  Table 1 presents the recommended values of yellow change and red clearance intervals for posted speeds of 25 mph to 55 mph and for intersection widths up to 110 feet.  The red clearance intervals are calculated based on the equation minus 1 second to account for conflicting movement startup loss  time.    For  intersections  greater  than 110  feet  (including  SPUI’s) or  speeds  less  than 25 mph engineering calculations shall be used to determine red clearances on a case by case basis and shall be  accepted by  a NMDOT  Traffic  Technical  Support  Engineer.   However,  it  should be noted  that according  to  the  ITE  Traffic  Signal  Timing  Manual,  typical  practice  incorporates  red  clearances ranging from 0.5 seconds to 2.0 seconds.  All calculations are rounded up to nearest 0.5 seconds.  

 Table 1 – Recommended Yellow Change and Red Clearance Interval values 

 

50 60 70 80 90 100 110

25 3.0 1.0 1.0 1.0 1.5 1.5 2.0 2.0

30 3.5 1.0 1.0 1.0 1.0 1.5 1.5 1.5

35 4.0 1.0 1.0 1.0 1.0 1.0 1.0 1.5

40 4.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0

45 4.5 1.0 1.0 1.0 1.0 1.0 1.0 1.0

50 5.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0

55 5.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0

Width of Intersection (ft)

Red Clearance Interval (s)

Posted Speed 

(MPH)

Yellow Change 

Interval (s)*

 *Yellow change interval does not account for downgrade approaches.  If significant downgrades are present, use equation with grade adjustment. 

 For deviations from the methods described herein, the length of the yellow vehicle change interval and the red clearance interval shall be approved by a NMDOT Traffic Technical Support Engineer.   Further  information  on  Yellow  Change  and  Red  Clearance  Intervals  is  referenced  in  the  Section 4D.26 of 2009 MUTCD (provided in Appendix 1).  

 Pedestrian Intervals  NMDOT policy of calculation of pedestrian  intervals  is based on the 2009 Edition of the Manual of Uniform Traffic Control Devices. NMDOT uses Countdown Pedestrian Signals as standard  (refer  to Section 4E.07 of 2009 MUTCD for operational instructions).   The recommended pedestrian interval is the sum of pedestrian walk interval and pedestrian change interval.   Pedestrian Walk Interval  Pedestrian walk  interval  is  the  time  for which  a  steady WALKING  PERSON  (symbolizing WALK)  is displayed  on  a  pedestrian  signal  head.  A  7  second  walk  interval  is  recommended  so  that pedestrians will  have  adequate  opportunity  to  leave  the  curb  or wheelchair  ramp  before  the pedestrian change interval begins. A walk interval of 4 seconds may be sufficient when fewer than 10  pedestrians  per  cycle  are  expected  or where  it  is  desired  to  favor  the  length  of  an  opposing phase.  A  walk  interval  of  7  seconds  or  more  may  be  used  for  moderate  to  heavy  pedestrian volumes.  Pedestrian Change Interval  A pedestrian change  interval  is  the  time  for which a  flashing UPRAISED HAND  (symbolizing DONT WALK) signal indication and countdown time are displayed on the pedestrian signal head. Following the pedestrian change interval, a buffer interval consisting of a steady UPRAISED HAND (symbolizing DONT WALK)  signal  indication  shall  be  displayed  for  at  least  3  seconds  prior  to  release  of  any conflicting vehicular movement. Pedestrian  change  interval  is  calculated based on  the pedestrian clearance time less the buffer interval. The pedestrian clearance time is the length of time estimated to walk across the street at normal walking speed. The buffer interval should be equal to the yellow change  interval  of  the  vehicular  signal  phase  provided  for  vehicles  travelling  parallel  to  the pedestrian crosswalk direction.  

3

4

  The following equation shall be used to calculate the pedestrian change interval:  Pedestrian Change  Interval = Pedestrian Clearance Time  (P/w)  ‐ Buffer  Interval  (Y)  (rounded up  to nearest whole second)         where:  P = distance from curb to curb or center of wheelchair ramp to center of wheelchair 

ramp along center of crosswalk (feet)     w = normal walking speed   Y = Yellow change interval of vehicular signal phase parallel to crosswalk direction.  For new signal installations and modified signal installations the NMDOT policy recommends the use of extended pedestrian phase pushbutton  functionality.   A standard pedestrian pushbutton activation  will  prompt  a  pedestrian  clearance  time  based  on  the  above  equation  and  4.0 feet/second  walking  speed.    An  extended  pedestrian  pushbutton  activation  will  prompt  a pedestrian clearance time based on the above equation and 3.5 feet/second walking speed.  This policy  will  require  additional  setting  configuration  in  the  controller  to  allow  for  extended pedestrian phase pushbutton functionality and a MUTCD R10‐32p sign denoting this functionality is in use.  Existing signal  locations may remain as  is or be upgraded at the discretion of the NMDOT Traffic Technical  Support  Section.    Recommended  walking  speed  for  installations  without  extended pushbutton functionality is 3.5 feet/sec.  Additional  consideration  could  be  given  to  pedestrian  signal  indications  near  facilities  that  serve segments  of  the  population with  slower walking  speeds.    In  this  case walking  speeds  should  be calculated based on a  lower walking speed. Such populations should be anticipated near shopping centers, convalescent or rest homes, therapy centers, elementary schools, etc.  A walking speed of 3.0 ft/sec should be considered if senior citizens or school children are in the majority at a specific crosswalk.     Walking  speeds below  3.5  ft/sec  shall be  approved by  a NMDOT  Traffic  Technical Support Engineer. 

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Table 2 presents recommended values of pedestrian clearance time for various walking speed and pedestrian crossing distance values. Buffer interval should be subtracted from pedestrian clearance time to determine pedestrian change interval.    

 Table 2 – Recommended Pedestrian Clearance Time Values 

 

Walking Speed, (ft/sec) 

3.0  3.5  4.0 

Pedestrian Crossing 

Distance, P (ft) 

Pedestrian Change Interval (sec) 

20  7  6  5 

25  8  7  6 

30  10  9  8 

35  12  10  9 

40  13  11  10 

45  15  13  11 

50  17  14  13 

60  20  17  15 

70  23  20  18 

80  27  23  20 

90  30  26  23 

100  33  29  25 

110  37  31  28 

120  40  34  30 

130  43  37  33 

 

Figure 4E‐2  in  the 2009 Manual of Uniform  Traffic Control Devices  shows pedestrian  intervals  in relations to the vehicular signal intervals.  

  On a street which has an island or median of 6 feet or greater width, the pedestrian clearance time may be computed to provide only enough time to clear the crossing from the curb to the median; in such  cases,  an  additional  detector  shall  be  provided  on  the  island.  Where  median‐mounted pedestrian  signals and detectors are provided,  the use of accessible pedestrian  signals  should be considered (refer Section 4E.05 of 2009 MUTCD).   During the transition into preemption, the walk interval and the pedestrian change interval may be shortened or omitted as described in Section 4D.27 of 2009 MUTCD.   If a leading pedestrian interval is used, the use of accessible pedestrian signals should be considered (Refer to Sections 4E.09 through 4E.13 of 2009 MUTCD)  Further  information  on  Pedestrian  Intervals  is  referenced  in  the  Section  4E.06  of  2009 MUTCD (provided in the Appendix 2).  Appendix 1 – Section 4D.26 of 2009 MUTCD  Appendix 2 ‐ Section 4E.06 of 2009 MUTCD  

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Dilemma Zone Protection Signalized intersection approaches with highly variable approach speeds greater than or equal to 45 mph, can exhibit safety  issues  in the form of what  is known as a dilemma zone or  indecision zone where  drivers  approaching  the  intersection  are  confronted with  a  choice  of whether  to  stop  or continue  through  the  intersection upon  the onset of a yellow  change  interval.   The dilemma  can occur at a point, depending on the approach speed, where the approaching vehicle can neither stop safely at the stop bar nor clear the intersection before the start of a conflicting green phase.  A more detailed  discussion  of  the  dilemma  zone  can  be  found  on  pages  4‐25  to  4‐32  in  the  FHWA publication Traffic Detector Handbook‐2006 and found in Appendix 3.    The  dilemma  zone  effect  at  high  speed  signalized  approaches  can  be  reduced  by  incorporating advanced detection to prompt the traffic signal controller to find an acceptable gap to terminate the active phase by extend the green phase to allow an approaching vehicle through the dilemma zone or by extending the all red clearance interval.  When considering extending the all red phase, further traffic  analysis  of  the  intersection  and  consultation  with  a  NMDOT  Traffic  Technical  Support Engineer is recommended.  Candidate  locations  have  an  approach  speed  of  45  mph  or  greater  and  are  typically  on  non‐coordinated  signal phases.    It  should be noted,  since dilemma  zone protection uses  green phase extensions and vehicle gap  identification as a means of  reducing dilemma zone  impacts, dilemma zone protection has limited effectiveness when applied to signal phases in a coordinated system, as these  phases  are  typically  set  to  run  their maximum  allotted  time  for  the  greatest  coordinated throughput.   Also  coordinated  phases  encourage  the  formation  of  platoons which  reduce  speed variability; therefore reducing the  likelihood of vehicles within the dilemma zones.   Dilemma zone protection  can  be  effective  on  a  coordinated  system  during  off‐peak  (uncoordinated)  hours  and possibly during coordinated hours with advanced controllers and controller logic programming.  The advanced programming allows the traffic signals to run  in coordination, with a window at the yield point  of  the  coordinated  phases  where  the  traffic  signal  detectors  on  the  main  line  become actuated.    Two  suggested  infrastructure  deployment  options  are  recommended  to  provide  dilemma  zone detection; traditional advance loop detection and the use of Continuous Tracking Advance Detectors (CTADs).  Deployment Option 1) Advance Loop Detection Applying advance  loop detection concepts derived  from  the Traffic Detector Handbook  (published by  the  FHWA),  Traffic  Signal Operations  Handbook  (published  by  ITE),  and  Traffic  Signal  Timing Manual  (published  by  ITE),  Table  3  and  Figure  2.  indicate  advance  loop  layouts  for  given  85th percentile speeds and are comparable with current practice of other DOT’s.  It should be noted that 85th  percentile  speeds  should  be  determined  based  on  speed  data  collected  on  the  approach  in question and confirmed with a NMDOT Traffic Technical Support Engineer. The recommended detector placements assume the following: 

Braking  reaction  time  is  1.5  seconds.    This  is more  conservative  the  1  second used  in  at 

many entities. 

Advanced detectors are 6 feet by 6 feet. 

Per AASHTO, a comfortable deceleration rate of 11.2 ft/s2 is applied. 

Passage Time is 2 seconds 

Detection mode is presence non‐locking mode. 

Stop bar detection can remain  in place. For stop bar detection standards, please reference 

NMDOT standard signal drawings. 

AASHTO Green Book equation for braking distance (Equation 3‐2) 

Table 3.  Advanced Loop Detector Placement for High Speed Approaches 

 

85th Percentile Speed

Speed Range

(MPH) (MPH) D1 D2 D3

70 50 to 70 625 480 350

65 45 to 65 550 415 295

60 40 to 60 480 350 240

55 35 to 55 415 295 195

50 40 to 50 ‐ 350 240

45 35 to 45 ‐ 295 195

Advanced Detector Setback

(Feet from Stop Bar)

  

Figure 2.  Advance Loop Detector Placement Dimensions 

 

 

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Deployment Option 2) Continuous Tracking Advance Detectors (CTAD’s) CTAD’s are  radar detectors mounted on  road side poles  tracking a variety of upstream  inputs such as vehicular speed, vehicle headways, and estimated time of arrival (ETA) to the stop bar.  These  data  inputs  are  used  to  determine  if  additional  green  time  is  needed  to  get  vehicles through the dilemma zone and when to activate the yellow phase.    The detection range at current NMDOT  installations  for the CTAD’s are 500  feet  longitudinally and 400 feet laterally.  However, depending on the product manufacturer, this detection range can vary and should be verified for design.   Recommended CTAD placements should cover the dilemma zone ranges for various 85th percentile speeds provided in Table 4. 

 Table 4.  CTAD Dilemma Zone Coverage Requirement 

 85th Percentile Dilemma Zone 

Speed (MPH) Coverage

(Feet from stop Bar)

70 195 to 625

65 195 to 550

60 195 to 480

55 195 to 415

50 195 to 350

45 195 to 295   

Optional Advance Warning and Dilemma Zone Protection with CTAD’s Flashing beacons can be deployed in conjunction with the CTAD’s as mitigation for intersections experiencing red light running and can be beneficial for traffic with longer braking distances like truck trailers providing additional warning and thus more time  to safely stop at a red  light.    If this type of installation is desired, the CTAD with warning beacon is recommended to be placed 3  seconds  in  advance  of  the  beginning  of  the  85th  percentile  speed  dilemma  zone.    Table  5 indicates CTAD with warning beacon placement locations in feet from the beginning of the 85th percentile speed dilemma zone.  

Table 5.  CTAD with Warning Beacon Placement  

85th Percentile CTAD and Warning Beacon

Speed (MPH) Placement

(Feet upstream of dilemma zone)

70 310

65 290

60 265

55 245

50 220

45 200   It should be noted that the passage time setting on the controller should be set at 3 seconds.  The Warning Flasher will be  set  to activate  three  seconds prior  to  the yellow phase, which  is designed to occur simultaneously as the detected vehicle enters the dilemma zone.

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APPENDIX 1

2009 MUTCD Yellow and Red Clearance Interval Excerpt

2009 Edition Page 485

on the approach, the signal faces for the approach shall be as described in Items B.1 and B.2, except that flashing YELLOW ARROW signal indications shall be used in place of the GREEN ARROW signal indications for the turning movement(s) that conflicts with the signalized vehicular or pedestrian movement.

Support:05 Figure 4D-20 illustrates application of these Standards on approaches that have only a shared

left-turn/right-turn lane, and on approaches that have one or more exclusive turn lanes in addition to the shared left-turn/right-turn lane.Option:

06 If the lane-use regulations on an approach are variable such that at certain times all of the lanes on the approach are designated as exclusive turn lanes and no lane is designated as a shared left-turn/right-turn lane: A. During the times that no lane is designated as a shared left-turn/right-turn lane, the left-turn and right-turn

movements may start and terminate independently, and the left-turn and right-turn movements may be operated in one or more of the modes of operation as described in Sections 4D.17 through 4D.24; and

B. If a protected-permissive mode is used, the shared left-turn/right-turn signal face provided in Paragraph 4 may be modified to include a dual-arrow signal section capable of displaying both a GREEN ARROW signal indication and a flashing YELLOW ARROW signal indication for a turn movement(s) in order to not exceed the maximum of five sections per signal face provided in Section 4D.08.

Section 4D.26 Yellow Change and Red Clearance IntervalsStandard:

01 A steady yellow signal indication shall be displayed following every CIRCULAR GREEN or GREEN ARROW signal indication and following every flashing YELLOW ARROW or flashing RED ARROW signal indication displayed as a part of a steady mode operation. This requirement shall not apply when a CIRCULAR GREEN, a flashing YELLOW ARROW, or a flashing RED ARROW signal indication is followed immediately by a GREEN ARROW signal indication.

02 The exclusive function of the yellow change interval shall be to warn traffic of an impending change in the right-of-way assignment.

03 The duration of the yellow change interval shall be determined using engineering practices.Support:

04 Section 4D.05 contains provisions regarding the display of steady CIRCULAR YELLOW signal indications to approaches from which drivers are allowed to make permissive left turns.Guidance:

05 When indicated by the application of engineering practices, the yellow change interval should be followed by a red clearance interval to provide additional time before conflicting traffic movements, including pedestrians, are released.Standard:

06 When used, the duration of the red clearance interval shall be determined using engineering practices.Support:

07 Engineering practices for determining the duration of yellow change and red clearance intervals can be found in ITE’s “Traffic Control Devices Handbook” and in ITE’s “Manual of Traffic Signal Design” (see Section 1A.11).Standard:

08 The durations of yellow change intervals and red clearance intervals shall be consistent with the determined values within the technical capabilities of the controller unit.

09 The duration of a yellow change interval shall not vary on a cycle-by-cycle basis within the same signal timing plan.

10 Except as provided in Paragraph 12, the duration of a red clearance interval shall not be decreased or omitted on a cycle-by-cycle basis within the same signal timing plan.Option:

11 The duration of a red clearance interval may be extended from its predetermined value for a given cycle based upon the detection of a vehicle that is predicted to violate the red signal indication.

12 When an actuated signal sequence includes a signal phase for permissive/protected (lagging) left-turn movements in both directions, the red clearance interval may be shown during those cycles when the lagging left-turn signal phase is skipped and may be omitted during those cycles when the lagging left-turn signal phase is shown.

December 2009 Sect. 4D.25 to 4D.26

2009 Edition Page 489

13 The duration of a yellow change interval or a red clearance interval may be different in different signal timing plans for the same controller unit.Guidance:

14 A yellow change interval should have a minimum duration of 3 seconds and a maximum duration of 6 seconds. The longer intervals should be reserved for use on approaches with higher speeds.

15 Except when clearing a one-lane, two-way facility (see Section 4H.02) or when clearing an exceptionally wide intersection, a red clearance interval should have a duration not exceeding 6 seconds.Standard:

16 Except for warning beacons mounted on advance warning signs on the approach to a signalized location (see Section 2C.36), signal displays that are intended to provide a “pre-yellow warning” interval, such as flashing green signal indications, vehicular countdown displays, or other similar displays, shall not be used at a signalized location.Support:

17 The use of signal displays (other than warning beacons mounted on advance warning signs) that convey a “pre-yellow warning” have been found by research to increase the frequency of crashes.

Section 4D.27 Preemption and Priority Control of Traffic Control SignalsOption:

01 Traffic control signals may be designed and operated to respond to certain classes of approaching vehicles by altering the normal signal timing and phasing plan(s) during the approach and passage of those vehicles. The alternative plan(s) may be as simple as extending a currently displayed green interval or as complex as replacing the entire set of signal phases and timing.Support:

02 Preemption control (see definition in Section 1A.13) is typically given to trains, boats, emergency vehicles, and light rail transit.

03 Examples of preemption control include the following: A. The prompt displaying of green signal indications at signalized locations ahead of fire vehicles, law

enforcement vehicles, ambulances, and other official emergency vehicles; B. A special sequence of signal phases and timing to expedite and/or provide additional clearance time for

vehicles to clear the tracks prior to the arrival of rail traffic; and C. A special sequence of signal phases to display a steady red indication to prohibit turning movements

toward the tracks during the approach or passage of rail traffic.04 Priority control (see definition in Section 1A.13) is typically given to certain non-emergency vehicles such as

light-rail transit vehicles operating in a mixed-use alignment and buses.05 Examples of priority control include the following:

A. The displaying of early or extended green signal indications at an intersection to assist public transit vehicles in remaining on schedule, and

B. Special phasing to assist public transit vehicles in entering the travel stream ahead of the platoon of traffic.06 Some types or classes of vehicles supersede others when a traffic control signal responds to more than one

type or class. In general, a vehicle that is more difficult to control supersedes a vehicle that is easier to control.Option:

07 Preemption or priority control of traffic control signals may also be a means of assigning priority right-of-way to specified classes of vehicles at certain non-intersection locations such as on approaches to one-lane bridges and tunnels, movable bridges, highway maintenance and construction activities, metered freeway entrance ramps, and transit operations.Standard:

08 During the transition into preemption control: A. The yellow change interval, and any red clearance interval that follows, shall not be shortened or

omitted. B. The shortening or omission of any pedestrian walk interval and/or pedestrian change interval shall

be permitted. C. The return to the previous green signal indication shall be permitted following a steady yellow

signal indication in the same signal face, omitting the red clearance interval, if any.

December 2009 Sect. 4D.26 to 4D.27

APPENDIX 2

2009 MUTCD Pedestrian Clearance Excerpt

Section 4E.06 Pedestrian Intervals and Signal Phases

Standard:01 At intersections equipped with pedestrian signal heads, the pedestrian signal indications shall bedisplayed except when the vehicular traffic control signal is being operated in the flashing mode. Atthose times, the pedestrian signal indications shall not be displayed.

02 When the pedestrian signal heads associated with a crosswalk are displaying either a steadyWALKING PERSON (symbolizing WALK) or a flashing UPRAISED HAND (symbolizing DONT WALK) signalindication, a steady or a flashing red signal indication shall be shown to any conflicting vehicularmovement that is approaching the intersection or midblock location perpendicular or nearlyperpendicular to the crosswalk.

03 When pedestrian signal heads are used, a WALKING PERSON (symbolizing WALK) signal indicationshall be displayed only when pedestrians are permitted to leave the curb or shoulder.

04 A pedestrian change interval consisting of a flashing UPRAISED HAND (symbolizing DONT WALK)signal indication shall begin immediately following the WALKING PERSON (symbolizing WALK) signalindication. Following the pedestrian change interval, a buffer interval consisting of a steadyUPRAISED HAND (symbolizing DONT WALK) signal indication shall be displayed for at least 3 secondsprior to the release of any conflicting vehicular movement. The sum of the time of the pedestrianchange interval and the buffer interval shall not be less than the calculated pedestrian clearancetime (see Paragraphs 7 through 16). The buffer interval shall not begin later than the beginning ofthe red clearance interval, if used.

Option:05 During the yellow change interval, the UPRAISED HAND (symbolizing DON'T WALK) signal indicationmay be displayed as either a flashing indication, a steady indication, or a flashing indication for aninitial portion of the yellow change interval and a steady indication for the remainder of the interval.

Support:06 Figure 4E-2 illustrates the pedestrian intervals and their possible relationships with associatedvehicular signal phase intervals.

Figure 4E-2 Pedestrian Intervals

Thumbnail image of Figure 4E-2

Guidance:07 Except as provided in Paragraph 8, the pedestrian clearance time should be sufficient to allow apedestrian crossing in the crosswalk who left the curb or shoulder at the end of the WALKINGPERSON (symbolizing WALK) signal indication to travel at a walking speed of 3.5 feet per second toat least the far side of the traveled way or to a median of sufficient width for pedestrians to wait.

Option:08 A walking speed of up to 4 feet per second may be used to evaluate the sufficiency of thepedestrian clearance time at locations where an extended pushbutton press function has beeninstalled to provide slower pedestrians an opportunity to request and receive a longer pedestrianclearance time. Passive pedestrian detection may also be used to automatically adjust the pedestrian

clearance time based on the pedestrian's actual walking speed or actual clearance of the crosswalk.

09 The additional time provided by an extended pushbutton press to satisfy pedestrian clearancetime needs may be added to either the walk interval or the pedestrian change interval.

Guidance:10 Where pedestrians who walk slower than 3.5 feet per second, or pedestrians who usewheelchairs, routinely use the crosswalk, a walking speed of less than 3.5 feet per second should beconsidered in determining the pedestrian clearance time.

11 Except as provided in Paragraph 12, the walk interval should be at least 7 seconds in length sothat pedestrians will have adequate opportunity to leave the curb or shoulder before the pedestrianclearance time begins.

Option:12 If pedestrian volumes and characteristics do not require a 7-second walk interval, walk intervalsas short as 4 seconds may be used.

Support:13 The walk interval is intended for pedestrians to start their crossing. The pedestrian clearance timeis intended to allow pedestrians who started crossing during the walk interval to complete theircrossing. Longer walk intervals are often used when the duration of the vehicular green phaseassociated with the pedestrian crossing is long enough to allow it.

Guidance:14 The total of the walk interval and pedestrian clearance time should be sufficient to allow apedestrian crossing in the crosswalk who left the pedestrian detector (or, if no pedestrian detector ispresent, a location 6 feet from the face of the curb or from the edge of the pavement) at thebeginning of the WALKING PERSON (symbolizing WALK) signal indication to travel at a walking speedof 3 feet per second to the far side of the traveled way being crossed or to the median if a two-stage pedestrian crossing sequence is used. Any additional time that is required to satisfy theconditions of this paragraph should be added to the walk interval.

Option:15 On a street with a median of sufficient width for pedestrians to wait, a pedestrian clearance timethat allows the pedestrian to cross only from the curb or shoulder to the median may be provided.

Standard:16 Where the pedestrian clearance time is sufficient only for crossing from the curb or shoulder to amedian of sufficient width for pedestrians to wait, median-mounted pedestrian signals (withpedestrian detectors if actuated operation is used) shall be provided (see Sections 4E.08 and 4E.09)and signing such as the R10-3d sign (see Section 2B.52) shall be provided to notify pedestrians tocross only to the median to await the next WALKING PERSON (symbolizing WALK) signal indication.

Guidance:17 Where median-mounted pedestrian signals and detectors are provided, the use of accessiblepedestrian signals (see Sections 4E.09 through 4E.13) should be considered.

Option:18 During the transition into preemption, the walk interval and the pedestrian change interval may beshortened or omitted as described in Section 4D.27.

19 At intersections with high pedestrian volumes and high conflicting turning vehicle volumes, a briefleading pedestrian interval, during which an advance WALKING PERSON (symbolizing WALK) indicationis displayed for the crosswalk while red indications continue to be displayed to parallel through and/orturning traffic, may be used to reduce conflicts between pedestrians and turning vehicles.

Guidance:20 If a leading pedestrian interval is used, the use of accessible pedestrian signals (see Sections

4E.09 through 4E.13) should be considered.

Support:21 If a leading pedestrian interval is used without accessible features, pedestrians who are visuallyimpaired can be expected to begin crossing at the onset of the vehicular movement when drivers arenot expecting them to begin crossing.

Guidance:22 If a leading pedestrian interval is used, it should be at least 3 seconds in duration and should betimed to allow pedestrians to cross at least one lane of traffic or, in the case of a large cornerradius, to travel far enough for pedestrians to establish their position ahead of the turning trafficbefore the turning traffic is released.

23 If a leading pedestrian interval is used, consideration should be given to prohibiting turns acrossthe crosswalk during the leading pedestrian interval.

Support:24 At intersections with pedestrian volumes that are so high that drivers have difficulty finding anopportunity to turn across the crosswalk, the duration of the green interval for a parallel concurrentvehicular movement is sometimes intentionally set to extend beyond the pedestrian clearance time toprovide turning drivers additional green time to make their turns while the pedestrian signal head isdisplaying a steady UPRAISED HAND (symbolizing DONT WALK) signal indication after pedestrianshave had time to complete their crossings.

APPENDIX 3

ITE Traffic Signal Timing Manual Excerpt

FHWA Traffic Detector Handbook - 2006 Excerpt

TXDOT Traffic Signal Operations Handbook - 2009 Excerpt

FHWA Traffic Detector Handbook - 2006 Excerpt

TXDOT Traffic Signal Operations Handbook - 2009 Excerpt