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51 eliminates exposure to vehicular traffic. These grade-separated crossings can improve safety and are desirable at some loca- tions. However, because grade-separated crossings can be quite expensive, may be considered unattractive, can poten- tially become sites of crime or vandalism, and may even decrease safety if not appropriately located and designed, these types of facilities are primarily used as measures of last a) J-Turn Intersection resort. The AASHTO Bicycle Guide (1999) provides guidance on the design of overpasses and underpasses. This strategy is related to Strategy 9.1 A5--Install Overpasses/Underpasses in NCHRP Report 500, Volume 10: A Guide for Reducing Colli- sions Involving Pedestrians (Zegeer et al. 2004). FHWA's Signalized Intersections: Informational Guide (Rodegerdts et al. 2004) advises that "pedestrian facilities should be provided at all intersections in urban and suburban b) Offset T-Intersection areas. In general," the authors say, "design of the pedestrian facilities of an intersection with the most challenged users in mind--pedestrians with mobility or visual impairments-- should be done, and the resulting design will serve all pedes- trians well." The Guide adds that the "ADA requires that new and altered facilities constructed by, on behalf of, or for the use of State and local government entities be designed and constructed to be readily accessible to and usable by indi- c) Left-Turn Median Acceleration Lanes viduals with disabilities." FHWA's guidelines are based on the premise that "pedestrians are faced with a number of dis- incentives to walking, including centers and services located far apart, physical barriers and interruptions along pedestrian routes, a perception that routes are unsafe owing to motor vehicle conflicts and crime, and routes that are [aestheti- cally] unpleasing." FHWA notes "key elements that affect a d) Offset Right-Turn Lane pedestrian facility that practitioners should incorporate into their design: FIGURE 18 Diagrams of median intersection designs on rural expressways (based on Maze et al. 2010). Keep corners free of obstructions to provide enough room for pedestrians waiting to cross. Maintain adequate lines of sight between drivers and However, the TLSI showed significant delay when traffic pedestrians on the intersection corner and in the cross- volumes on the major and minor roads are significantly dif- walk. ferent, and it operated most efficiently when the two crossing Ensure curb ramps, transit stops (where applicable), push- roads had similar volumes of traffic. buttons, etc., are easily accessible and meet ADAAG design standards. Pedestrian and Bicycle Facilities Clearly indicate the actions pedestrians are expected to take at crossing locations. According to NCHRP Report 500, Volume 18 (Raborn et al. Design corner radii to ensure vehicles do not drive over 2008), there are several ways to modify the geometry of an the pedestrian area yet are able to maintain appropriate intersection to improve bicycle safety, including: turning speeds. Ensure crosswalks clearly indicate where crossings should "Reducing the crossing distance for bicyclists. occur and are in desirable locations. Realigning intersection approaches to reduce or elimi- Provide appropriate intervals for crossings and minimize nate intersection skew. wait time. Modifying the geometry to facilitate bicycle movement Limit exposure to conflicting traffic and provide refuges at interchange on-ramps and off-ramps. where necessary. Providing refuge islands and raised medians." Ensure the crosswalk is a direct continuation of the pedestrian's travel path. At path/roadway intersections, an overpass or underpass Ensure the crossing is free of barriers, obstacles, and allows for uninterrupted flow for bicyclists and completely hazards."