Because of the variability in locating ramps, there are no specific requirements, only suggested guidelines:

• SHA preference is to utilize paired perpendicular ramps, (two ramps on each corner). While this is more easily accomplished on intersections of smaller radius, seek to apply this approach more broadly. Large diagonal ramps tend to mislead pedestrians who are blind.
• Often a minimum radius in urban areas is 35’. Given a 35’ radius, 10’ crosswalk and 4’ offset to stop bar, the pedestrian ramp will likely end up on the radius. If the ramp is on the radius, and must be perpendicular to the curbline, then the ramp will be skewed relative to the crosswalk. For traffic operations and sight distance for right turning vehicles, stop bars and crosswalks are often placed closer to the intersecting street, forcing the cross walk into the radius.
• On skewed intersections, paired perpendicular ramps may be the best solution for one corner, while a diagonal ramp may be the best solution for others.

FIGURE 2

The above figure shows;

• Major Streets - A curb extension or 'Bulb' with a 35' radius allows a single unit truck or bus to turn with minimum encroachment on adjacent lanes. Pedestrian crossings are shrtened and sidewalk space increases. Vehicle speeds are reduced.
• Minor Streets - A 'Bulb' improves pedestrian space but restricts turning vehicles larger than a passenger car.
• Pedestrian Safety - Bulbing allows greater visibility and increases reaction time.
• Advantages of 'Bulbing':
  • Allows easier retofit
  • Space for landscaping
  • Shorter / quicker pedestrian crossing
  • Prevents parking at the intersection

Quadrant A represents a larger radius to support SU vehicles, common for deliveries in residential areas. The ramps are forced onto the radius, posing complication for blind pedestrians. These ramps should be pushed toward the point of curvature – but not so far back as to adversely affect the location of the stop bar and crosswalk.

Quadrant B represents a smaller radius – more pedestrian friendly because the ramps are constructed parallel to the crosswalk. The disadvantage is that the radius supports only passenger cars.

Various ramp types are acceptable. Based upon the Accessible Rights-of-Way Design Guide, the following ramp types are available: (See Figure 3 and Table 1)

FIGURE 3

Use the following as guidance for selection and location of ramps.

TABLE 1

	Perpendicular	Diagonal	Parallel	Diagonal Parallel Combination	Perpendicular Parallel Combination
SW - 8’ & less from curb to back of walk			X	X
SW - 8’ to 12’ from curb to back of walk			X	X	X
SW - 12’ & more from curb to back of walk	X	X	X	X	X
Small Radius (20’ and Less)	X		X		X
Large Radius (25’ and Greater)		X	X	X
Islands	X				X