Potential MUTCD Criteria for Selecting the Type of Control for Unsignalized Intersections (2015)

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51 CHAPTER 5: CRITICAL REVIEW REVIEW OF MUTCD Sections 2B.04, 2B.06, and 2B.07 of the MUTCD contain numeric criteria for selecting unsignalized intersection traffic control. Key parts of the opening text, volume criteria, and sight distance criteria are reproduced in Table 20, while Table 21 shows the crash and combination criteria. Observations regarding the numeric and general criteria include the following:  The criteria are a combination of past practices and quantifiable traffic characteristics. However, there appears to be no research that directly supports the numerical criteria of these sections.  Some of the sections include bicycle and pedestrian volumes (Sections 2B.04 and 2B.07 for minor approaches only), while other sections only include vehicle volumes (Sections 2B.06 and 2B.07 for major approaches).  Bicycles are cited as a separate item in some, but not all, volume criteria. It is assumed that the criteria for vehicles include bicycles, but it is not clear. The MUTCD definition of a vehicle includes bicycles; a vehicle is defined in the MUTCD as “every device in, upon, or by which any person or property can be transported or drawn upon a highway, except trains and light rail transit operating in exclusive or semi-exclusive alignments. Light rail transit equipment operating in a mixed-use alignment, to which other traffic is not required to yield the right-of-way by law, is a vehicle.”  Pedestrian traffic is included in only selected volume criteria. Intersection pedestrian traffic is a portion of the volume considered for intersection conflicts and potentially needs more consideration. Guidance related to the application of pedestrian volumes is not adequate.  Crash criteria should only consider crashes that are susceptible to correction by the recommended treatment, as appropriately stated in the MUTCD sections. The magnitude of the number of crashes varied between the sections: five in 2 years in Section 2B.04 (YIELD or STOP sign), three in 1 year or five in 2 years in Section 2B.06 (STOP sign), and five in 1 year (multi-way STOP signs). While a difference should exist between Sections 2B.06 and 2B.07, how the criteria should differ between Section 2B.04 and the other two sections with numeric criteria is not as obvious.  Potential non-numeric criteria to install STOP signs could include the considerations listed in Table 22.  Section 2B.06 on STOP sign application is currently not sensitive to the difference between rural and urban conditions or the speed of the major street. It also does not discuss the differences in application between three- and four-leg intersections.  Currently, Section 2B.07 includes a 70 percent adjustment to cover higher-speed situations. This adjustment may be replaced with criteria developed based on the speed at the intersection.

52 Table 20. Opening Text and Criteria for MUTCD Sections with Numeric Criteria. Criteria 2B.04 Right-of-Way at Intersections 2B.06 STOP Sign Applications 2B.07 Multi-Way Stop Applications Opening Text …the use of YIELD or STOP signs should be considered at the intersection of two minor streets or local roads where the intersection has more than three approaches and where one or more of the following conditions exist: The use of STOP signs on the minor-street approaches should be considered if engineering judgment indicates that a stop is always required because of one or more of the following conditions: The following criteria should be considered in the engineering study for a multi-way STOP sign installation: Volume A. The combined vehicular, bicycle, and pedestrian volume entering the intersection from all approaches averages more than 2,000 units per day The vehicular traffic volumes on the through street or highway exceed 6,000 vehicles per day C. Minimum volumes: 1. The vehicular volume entering the intersection from the major street approaches (total of both approaches) averages at least 300 vehicles per hour for any 8 hours of an average day; and 2. The combined vehicular, pedestrian, and bicycle volume entering the intersection from the minor street approaches (total of both approaches) averages at least 200 units per hour for the same 8 hours, with an average delay to minor-street vehicular traffic of at least 30 seconds per vehicle during the highest hour; but 3. If the 85th-percentile approach speed of the major-street traffic exceeds 40 mph, the minimum vehicular volume warrants are 70 percent of the values provided in Items 1 and 2. Sight Distance B. The ability to see conflicting traffic on an approach is not sufficient to allow a road user to stop or yield in compliance with the normal right- of-way rule if such stopping or yielding is necessary A restricted view exists that requires road users to stop in order to adequately observe conflicting traffic on the through street or highway

53 Table 21. Sight Distance and Crash Criteria for MUTCD Sections with Numeric Criteria. Criteria 2B.04 Right-of-Way at Intersections 2B.06 STOP Sign Application 2B.07 Multi-Way Stop Applications Crashes C. Crash records indicate that five or more crashes that involve the failure to yield the right-of-way at the intersection under the normal right-of-way rule have been reported within a 2-year period C. Crash records indicate that three or more crashes that are susceptible to correction by the installation of a STOP sign have been reported within a 12-month period, or that five or more such crashes have been reported within a 2-year period. Such crashes include right-angle collisions involving road users on the minor-street approach failing to yield the right-of-way to traffic on the through street or highway. B. Five or more reported crashes in a 12-month period that are susceptible to correction by a multi-way stop installation. Such crashes include right- turn and left-turn collisions as well as right-angle collisions. Other Where no single criterion is satisfied, but where Criteria B, C.1, and C.2 are all satisfied to 80 percent of the minimum values. Criterion C.3 is excluded from this condition. Table 22. Suggested Considerations to Install a STOP Sign. Source Considerations 2009 MUTCD Section 2B.04 (Support, 09)  Controlling the direction that conflicts the most with established pedestrian crossing activity or school walking routes.  Controlling the direction that has obscured vision, dips, or bumps that already require drivers to use lower operating speeds.  Controlling the direction that has the best sight distance from a controlled position to observe conflicting traffic. 2009 MUTCD Section 2B.04 (Standard, 10)  If the signal indication for an approach is a flashing red at all times.  If a minor street or driveway is located within or adjacent to the area controlled by the traffic control signal, but does not require separate traffic signal control because an extremely low potential for conflict exists.  If a channelized turn lane is separated from the adjacent travel lanes by an island and the channelized turn lane is not controlled by a traffic control signal. 2009 MUTCD Section 2B.07 (Option, 05)  The need to control left-turn conflicts.  The need to control vehicle/pedestrian conflicts near locations that generate high pedestrian volumes.  Locations where a road user, after stopping, cannot see conflicting traffic and is not able to negotiate the intersection unless conflicting cross traffic is also required to stop.  An intersection of two residential neighborhood collector (through) streets of similar design and operating characteristics where multi-way stop control would improve traffic operational characteristics of the intersection. Other Suggestions from Research  Lower functional classification street intersects a higher functional class street.  Modal priority, for example, to establish a bike route.  To redirect traffic within a grid network.  To improve operations within a network.  SSIF program.

54 IDENTIFY INTERSECTION AND TRAFFIC CHARACTERISTICS The literature and state manual review tasks generated tables of the different methods being used to evaluate the need for STOP or YIELD signs at an intersection. The intersection, traffic, and safety characteristics required for these methods were identified to understand how these characteristics affect decisions made regarding traffic control. Most techniques include the following criteria for making traffic control decisions:  Functional class.  Vehicular volume (either approach or entering, measured per hour or ADT).  Reported crash experience.  Speed. The following criteria are also considered:  Sight distance available on each approach.  Angle of approach.  Geometric (e.g., in median, roundabouts, channelized right-turn lanes, and railroad grade crossings). Some also consider:  Volume (either approach or entering, measured per hour or ADT) of bicycles and pedestrians.  Delay.  Left-turn volume on major approaches.  Volume split (e.g., 60/40 for four-leg and 75/25 for three-leg intersections, or approximately equal). Other criteria mentioned but not obviously used in existing warrants include:  Queue length.  LOS. Additional criteria considered when making a pedestrian traffic control device decision at an unsignalized intersection include the following:  Crossing distance.  Number of lanes.  Distance to nearest signalized or all-way stop-controlled intersection.

55 SUGGESTIONS Suggestions regarding the numeric and general criteria include the following:  All numeric criteria should include consideration of pedestrians and bicycles or have justification for why these counts are not considered (e.g., they are considered in other criteria).  Potential, non-numeric reasons to install STOP signs could include the considerations suggested in Table 22.  The MUTCD should have both numeric criteria and non-numeric criteria (examples listed in Table 22). QUESTIONS Based on these observations, the following questions are raised:  Perhaps the numeric criteria within Section 2B.04 should be removed and the reader referred to Sections 2B.06 and 2B.07. Another approach could be to create a section that specifically addresses numeric criteria for YIELD sign or no control situations. Another suggestion is to have Section 2B.04 focus on non-numeric situations or focus on the local road (residential street) condition.  Should some or all of the criteria listed in Section 2B.07 (reproduced in Table 22) be considered at two-way stop-controlled intersections?  How should the need for STOP or YIELD signs at roundabouts or right-turn channelization lanes be discussed—within a non-numeric section, or should criteria be established?  If the number of legs at the intersection becomes a factor, how should the section address the condition when the predominant flow on the three-leg intersection is from the stem?  Another geometric concern is when the angle of intersection is less than 75 degrees as documented in several publications including the Handbook for Designing Roadways for the Aging Population (72). Is it sufficient to say that the sight distance check will cover the situation when a skew angle exists?  With greater use of the RRFB, there is a pressing need to understand how the device affects TWSC intersection operations and safety. Should the RRFB be considered in an HCM methodology to change the relative priorities of traffic streams to actually have pedestrians be the first priority? What effect would that have in the operations analysis? How should the RRFB be considered with respect to making a decision regarding TWSC or AWSC?  How should the procedure handle bicyclists that dismount and walk their bike across the intersection? Should this maneuver be considered a pedestrian or a vehicle (bicycle)?  Should the MUTCD explicitly address the question of whether to consider induced pedestrians—in other words, to increase the pedestrian count in recognition that the addition of the traffic control will result in additional pedestrians at the unsignalized intersection?  The criteria in the STOP sign section (Section 2B.06) do not appear to consider delay or queue length. Should this section include criteria that address either of these measures?  An approach used in Portland is to evaluate a series of intersections throughout the city to determine where pedestrian traffic is highest on streets that are difficult to cross. This is applied specifically on streets where a person crossing the street has died due to a crash. In

56 application, the location of the fatality, if likely to reduce the risk of future crashes, is selected. If a nearby location or downstream intersection is likely to reduce crashes further, a conversation with the community often ensues to determine the appropriate location. DIRECTION FOR PHASE II Based upon the review of the literature, policies, the existing criteria in the MUTCD, and discussions with practitioners, key considerations for the Phase II work plan included the following:  Set a higher priority on investigating when to go from TWSC to AWSC rather than when to go from no control to yield control or TWSC. Functional classification of the intersection approach legs is often used to determine no control, yield control, and TWSC.  Develop criteria that reflect urban and rural conditions and develop criteria based on speed. A similar comment was that local/residential streets in dense urban areas should have unique criteria rather than having the same criteria for both lower-speed and higher-speed roads or having the same criteria for both local/residential streets as compared to collectors/arterial streets.  Consider roundabouts as a geometric design alternative within the evaluation.  Include sight distance as a factor in the warrants.  Consider a variety of major- and minor-road volume splits and not just when the split is “approximately equal.”  Select an approach that will permit findings to be available by June 2014 so that the criteria may be considered for the next edition of the MUTCD.  Consider the existing and ongoing revisions to relevant sections of the MUTCD, such as the changes being proposed for defining “approximately equal” and the changes suggested for the reorganization. If resources permitted, the following were also to be considered:  Present a list of alternative treatment ideas (e.g., a beacon with a STOP sign or advance signing); however, NCHRP Project 3-109 should focus on the warrants for STOP signs and not on warrants for these alternative treatments.  Explore the concept of prioritization of traffic control installation based on risk (e.g., the likelihood of pedestrians in urban areas with higher speeds and assuming limited budgets to provide signs, beacons, and lighting).  Consider the presence of transit and sidewalks as a part of the process.