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Chapter 6: Overcoming barriers to safe design
Pages 60-82

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From page 60...
... Summary Practitioners may face physical constraints, competing stakeholder and user concerns, and limited resources when reallocating street space. When there is not enough space for all street users, provide safe access for everyone in three ways: • Reduce street speeds • Reduce motor vehicle volumes • Identify network opportunities When there is too much space, reduce vehicle speeds and exposure for vulnerable road users with cross-section elements like raised medians, wider buffers, and dynamic curbside uses.
From page 61...
... However, when minimum dimensions for multiple elements are used, they can create safety concerns that would not otherwise exist. A minimally narrow travel lane next to a minimally narrow parking lane puts moving motor vehicles too close to parked cars, which could result in crashes.
From page 62...
... In addition to through travel lanes, generalpurpose lanes may be dedicated right- or left-turn lanes or two-way left-turn lanes. Streets with general-purpose lanes may be two-way or one-way (Figure 7-2)
From page 63...
... Cross-Section Elements 7-3   Figure 7-2. Two-lane street with turn lanes in Portland, OR.
From page 64...
... As speeds and motor vehicle volumes increase, separating modes and providing more frequent crossing opportunities become imperative. Practitioners should prioritize separation by starting with users of the lowest-volume and lowest-speed modes and then working up: first pedestrians, then bicyclists, then motor vehicles, including freight and transit; each mode's users should be provided with bidirectional travel as that mode is separated.
From page 65...
... Other performance measures that can be used for selecting streets where dedicated lanes may work best include person throughput and average transit speed and reliability. Key Outcomes: Providing a bus lane can make transit more attractive by improving bus reliability and reducing transit travel times, providing increased access to businesses and commercial areas, and reducing transit operating costs.
From page 66...
... . Bus lanes can also be shared with other motor vehicles.
From page 67...
... or unidirectional bicycle facilities. One-way bike lanes on the outside of general-purpose travel lanes provide access to the destinations along that side of the street.
From page 68...
... . The higher the speed and volume of traffic on the adjacent roadway, the wider the buffer should be between motor vehicles and pedestrians on the sidewalk.
From page 69...
... Facility Type (Width) # of Travel Lanes Vehicle Volume (ADT)
From page 70...
... Facility Type (Width) # of Travel Lanes On-Street Parking Location (Additional Buffer Width)
From page 71...
... Table 7-6 provides guidance on the type of crossing treatment needed based on traffic context. As vehicle volumes and speeds get higher it becomes increasingly critical to provide signalized crossing opportunities.
From page 72...
... 7-12 Roadway Cross-Section Reallocation: A Guide 1,000 ft (3-4 blocks) Table 7-5.
From page 73...
... Cross-Section Elements 7-13   Applicability: Sidepaths are mainly applicable in areas with few motor vehicle driveways or access points and lower volumes of people walking and biking. Sidepaths can be used along higher-speed and/or higher-volume streets to provide a completely separated space outside of the street for pedestrians and bicyclists.
From page 74...
... One key concern with providing sidepaths instead of directional bicycle facilities is the lack of driver awareness about contraflow bicycle traffic (higher-speed traffic than pedestrians, who are expected to travel bidirectionally) at intersections and access points.
From page 75...
... Applicability: Medians are typically applicable where you have few access points, would like to restrict access, or have a history of crashes involving vehicles crossing the centerline, including head-on and le-turning crashes. Key Outcomes: Installation of medians helps to create pedestrian crossing refuges, controls turning movements, and reduces conflicting vehicle paths, thereby improving safety.
From page 76...
... Because medians restrict turns and corridor access, they remove friction along a corridor. Although this can have many positive safety benefits, it may also encourage drivers to move at higher speeds (Butorac et al.
From page 77...
... Cross-Section Elements 7-17   Figure 7-16. A flex post curb extension in Washington, DC.
From page 78...
... Figure 7-20. A street café along curb space in Baltimore, MD.
From page 79...
... Cross-Section Elements 7-19   Figure 7-22. A parklet along the curb in Baltimore, MD.
From page 80...
... will interact with adjacent cross-section elements such as bike lanes and sidewalks. These interactions need to be considered to ensure appropriate buffer space is provided.
From page 81...
... This chapter summarizes important steps in making cross-section changes and, with 10 case studies, provides examples of successful reallocation projects throughout the United States. The Role of Funding All street redesign efforts need funding to move from concept to reality.
From page 82...
... Design and Construction Any transportation agency can initiate and complete design processes to rebuild streets. The level of detail and number of phases in the design process vary based on project type, but street redesign projects generally include both preliminary and final design phases.


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