Roundabouts: An Informational Guide – Second Edition (2010) / Chapter Skim
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Pages 247-288
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Chapter 7/Application of Traffic Control Devices Page 7-1 Roundabouts: An Informational Guide CHAPTER 7 APPLICATION OF TRAFFIC CONTROL DEVICES CONTENTS 7.1 INTRODUCTION .
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Roundabouts: An Informational Guide Page 7-2 Chapter 7/Application of Traffic Control Devices LIST OF EXHIBITS Exhibit 7-1 Approach and Departure Pavement Markings .
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Chapter 7/Application of Traffic Control Devices Page 7-3 Roundabouts: An Informational Guide Exhibit 7-29 Examples of Metering Signals .
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Roundabouts: An Informational Guide Page 7-4 Chapter 7/Application of Traffic Control Devices 7.1 INTRODUCTION This chapter presents guidelines on the application of traffic control devices associated with roundabouts. The design installation of these elements is an important component in achieving the desired operational and safety features of a roundabout.
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Chapter 7/Application of Traffic Control Devices Page 7-5 Roundabouts: An Informational Guide These principles also extend to the designation of lanes on approaches to roundabouts: • Traffic volume considerations and roundabout operations. Roundabouts should be designed with the appropriate number and assignment of lanes to handle the expected through, left-turning, and right-turning traffic.
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Roundabouts: An Informational Guide Page 7-6 Chapter 7/Application of Traffic Control Devices double yellow lines. For small splitter islands [area less than 75 ft2 (7 m2)
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Chapter 7/Application of Traffic Control Devices Page 7-7 Roundabouts: An Informational Guide • Solid lane lines on approaches and departures can discourage drivers from cutting across multiple lanes to attain a faster path through the roundabout. Using solid lane lines throughout the area of deflection can be used to provide this benefit.
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Roundabouts: An Informational Guide Page 7-8 Chapter 7/Application of Traffic Control Devices give advance notice to cyclists that they need to merge, providing more room for them to achieve this maneuver and find an appropriate gap in traffic. On roundabout departures, a dotted line should be used through the diverging taper, and the solid bike lane line should resume as soon as the normal bicycle lane width is available.
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Chapter 7/Application of Traffic Control Devices Page 7-9 Roundabouts: An Informational Guide quickly lose their readability when a portion of the marking is worn away by the tires of passing vehicles. Where lane-use arrows are used on roundabout approaches, it is important that left-turn arrows be included.
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Roundabouts: An Informational Guide Page 7-10 Chapter 7/Application of Traffic Control Devices MUTCD (3B.20 and 3C.06)
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Chapter 7/Application of Traffic Control Devices Page 7-11 Roundabouts: An Informational Guide Exhibit 7-5 Roundabout Entrance Pavement Markings Exhibit 7-6 Example of Staggered Yield Line on a Multilane Approach Yield lines can be used to indicate where approaching vehicles should yield, supplementing the entrance lines. 7.3.1.6 Entrance and Yield Lines Dotted circulatory roadway edge line extensions should be used across the entry lanes of roundabouts, as illustrated in Exhibit 7-5.
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Roundabouts: An Informational Guide Page 7-12 Chapter 7/Application of Traffic Control Devices 7.3.1.7 Pedestrian Crosswalk Markings Pedestrian crosswalk markings should be installed at all pedestrian crossing locations at roundabouts in urban and suburban locations. Crosswalk markings provide guidance for pedestrians in navigating a roundabout and provide a visual cue to drivers of where pedestrians may be within the roadway.
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Chapter 7/Application of Traffic Control Devices Page 7-13 Roundabouts: An Informational Guide 7.3.2 CIRCULATORY ROADWAY PAVEMENT MARKINGS Circulatory roadway pavement markings consist of lane lines, edge lines, and lane-use arrows. Examples of these markings are shown in Exhibit 7-8, and the following sections discuss each of these types of markings in more detail.
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Roundabouts: An Informational Guide Page 7-14 Chapter 7/Application of Traffic Control Devices island, a normal-width white line should be used. Wide dotted edge line extensions should be placed across the entry lanes of roundabouts.
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Chapter 7/Application of Traffic Control Devices Page 7-15 Roundabouts: An Informational Guide the circulatory roadway would discourage drivers from crossing the lane line to enter the appropriate lane, so it is useful to have a dotted line across the approach. Some practitioners have raised concerns that if a solid line transitions to a dotted line at the approach as shown in the figures in Chapter 3C of the MUTCD and illustrated in Exhibit 7-9, circulating drivers might think that they are allowed to change lanes at the dotted line prior to exiting the roundabout.
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Roundabouts: An Informational Guide Page 7-16 Chapter 7/Application of Traffic Control Devices 7.3.2.3 Lane-Use Arrows Lane-use arrows within the circulatory roadway are an important component of the comprehensive system of signing and marking at roundabouts. These arrows provide confirmation to drivers, giving them confidence that they have entered in the correct lane and can continue circulating within this lane to get to their desired exit.
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Chapter 7/Application of Traffic Control Devices Page 7-17 Roundabouts: An Informational Guide described in Section 7.3.1.6. However, most mini-roundabouts are simple enough that entrance lines are sufficient for this purpose.
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Roundabouts: An Informational Guide Page 7-18 Chapter 7/Application of Traffic Control Devices 7.4.1 REGULATORY SIGNS A number of regulatory signs are appropriate for roundabouts and are described below. 7.4.1.1 Yield Sign A yield sign (R1-2)
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From page 265... ...
Chapter 7/Application of Traffic Control Devices Page 7-19 Roundabouts: An Informational Guide Roundabout Directional Arrow signs are preferred over One-Way signs for several reasons: • The black-and-white chevron design of the Roundabout Directional Arrow signs is unique and can only be used at roundabouts. Therefore, consistent and uniform use of this sign will serve to remind road users when they are entering a roundabout.
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Roundabouts: An Informational Guide Page 7-20 Chapter 7/Application of Traffic Control Devices 7.4.1.6 Intersection Lane-Control Signs For roundabouts with multiple entry lanes, as for any intersections with multiple entry lanes, drivers benefit from a consistent system of signing and marking telling them which lanes to use for the various left, through, and right movements. This is particularly important if the lane configuration is not consistent with the default rules of the road: left turns allowed only from the leftmost lane, right turns allowed only from the rightmost lane, and through movements allowed from any lane.
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Chapter 7/Application of Traffic Control Devices Page 7-21 Roundabouts: An Informational Guide of the lane-control signs adjacent to the corresponding lane-use arrow markings. An optional second set of lane designation signing (not shown in Exhibit 7-20)
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From page 268... ...
Roundabouts: An Informational Guide Page 7-22 Chapter 7/Application of Traffic Control Devices users that they are approaching an intersection with the form of a roundabout. This sign, introduced in the 2003 edition of the MUTCD, has many advantages over advance warning signs that have been used at roundabouts in the past: • It includes an easily recognizable symbol that is similar to the symbols used for roundabouts in other countries.
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Chapter 7/Application of Traffic Control Devices Page 7-23 Roundabouts: An Informational Guide 7.4.2.4 Other Warning Signs • Yield Ahead sign. The Yield Ahead sign (W3-2)
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Roundabouts: An Informational Guide Page 7-24 Chapter 7/Application of Traffic Control Devices Exhibit 7-18 Example of Regulatory and Warning Signs for Mini-Roundabouts Source: 2009 MUTCD (1) (Optional)
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Chapter 7/Application of Traffic Control Devices Page 7-25 Roundabouts: An Informational Guide Exhibit 7-19 Example of Regulatory and Warning Signs for SingleLane Roundabouts Source: 2009 MUTCD (1) (Optional)
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Roundabouts: An Informational Guide Page 7-26 Chapter 7/Application of Traffic Control Devices not necessary at local street roundabouts or in urban settings where the majority of users are likely to be familiar with the site. • Text exit destination signs.
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Chapter 7/Application of Traffic Control Devices Page 7-27 Roundabouts: An Informational Guide Exhibit 7-21 Exit Destination Signs with Text and Arrows Exhibit 7-22 Diagrammatic Exit Destination Sign Advance Street Name (D3-2) signs are sometimes installed in advance of roundabouts to provide road users with the name(s)
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Roundabouts: An Informational Guide Page 7-28 Chapter 7/Application of Traffic Control Devices should be considered in the selection of roadside mounting versus overhead mounting of guide signs. 7.4.3.2 Exit and Departure Signs Exit guide signs (D1–1d and D1-1e)
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Chapter 7/Application of Traffic Control Devices Page 7-29 Roundabouts: An Informational Guide 7.4.4 SUPPLEMENTAL TREATMENTS Some agencies in the United States are experimenting with the use of flexible, internally illuminated bollards as a means to highlight the leading edge of a splitter island, particularly at mini-roundabouts where the central island is less visible. This is a common application in the United Kingdom, where the illuminated bollards are combined with a Keep Left sign, as shown in Exhibit 7-26.
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Roundabouts: An Informational Guide Page 7-30 Chapter 7/Application of Traffic Control Devices Exhibit 7-27 Examples of Speed Reduction Treatments Exhibit 7-26 Internally Illuminated Bollard Cambridge, England, United Kingdom (a) Warning beacons (Leeds, Maryland)
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Chapter 7/Application of Traffic Control Devices Page 7-31 Roundabouts: An Informational Guide • Rumble strips placed in advance of the roundabout, • Speed-reduction markings placed transversely across travel lanes (see MUTCD Section 3B.22) , and • Vehicle-activated speed warning signs commonly triggered by speeds exceeding an acceptable threshold.
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Roundabouts: An Informational Guide Page 7-32 Chapter 7/Application of Traffic Control Devices Because of additional objectives and constraints, metering by upstream signals is generally not as effective as direct entrance metering. More than one entrance can be metered, and the analyst needs to identify operational states and evaluate each one separately to provide a weighted aggregate performance measure.
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Chapter 7/Application of Traffic Control Devices Page 7-33 Roundabouts: An Informational Guide 7.5.2 PEDESTRIAN SIGNALS AT ROUNDABOUTS There are several situations where it may be beneficial to signalize pedestrian crossings at roundabouts. At first it may seem contradictory to add pedestrian signals at roundabouts since roundabouts are often used as a preferred alternative to signalized intersections.
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Roundabouts: An Informational Guide Page 7-34 Chapter 7/Application of Traffic Control Devices Where two-stage pedestrian crossings are used, care must be taken in the design and placement of the pedestrian signals. If two pedestrian signals for different walk intervals can be seen from the nearside, pedestrians might see the wrong signal and inadvertently cross at the inappropriate time.
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Chapter 7/Application of Traffic Control Devices Page 7-35 Roundabouts: An Informational Guide wrong signal. If an offset is provided, it is beneficial to provide landscaping or a railing in the splitter island to guide pedestrians to the crosswalks.
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From page 282... ...
Roundabouts: An Informational Guide Page 7-36 Chapter 7/Application of Traffic Control Devices The signal would rest in green for motorists entering and exiting the roundabout, and the pedestrian signal head would display the steady upraised hand symbolizing "don't walk." When the signal is actuated by a pedestrian, the vehicle signal would change to yellow and then red, after which the pedestrian signal head displays a walking person symbolizing the walk interval and then the flashing upraised hand symbolizing the pedestrian clearance interval. The key design consideration when considering traditional red-yellow-green signals is the potential for motorist confusion between the green display at the crosswalk and the yield sign at the entry.
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Chapter 7/Application of Traffic Control Devices Page 7-37 Roundabouts: An Informational Guide activating the pedestrian signal if they so desire, which can further reduce delay to motor vehicles. 7.5.2.4 Other Displays There may be advantages to experimenting with other signal displays for pedestrian crossings at roundabouts to find the best solution.
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Roundabouts: An Informational Guide Page 7-38 Chapter 7/Application of Traffic Control Devices no need for left- or right-turn signal heads, post-mounted signals have often been deemed to be sufficient where signals are used at roundabouts. This is especially true at two-lane approaches to roundabouts where approaching drivers will have a post-mounted signal immediately adjacent to their lane.
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Chapter 7/Application of Traffic Control Devices Page 7-39 Roundabouts: An Informational Guide There are three common ways in which rails can interact with a roundabout: 1. Within the roadway median and through the center of the roundabout, 2.
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Roundabouts: An Informational Guide Page 7-40 Chapter 7/Application of Traffic Control Devices Exhibit 7-34 Rail Crossing One Leg of the Intersection (a) Gates at all Entries (b)
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Chapter 7/Application of Traffic Control Devices Page 7-41 Roundabouts: An Informational Guide Exhibit 7-35 Rail Crossing through Center of Roundabout (a) Gates at all Entries (b)
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Roundabouts: An Informational Guide Page 7-42 Chapter 7/Application of Traffic Control Devices 7.7 REFERENCES 1. Manual on Uniform Traffic Control Devices for Streets and Highways.
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