APPENDIX B (Continued)
Example 2. Referring to Figure B-1, the target buildings in this case are 796 and 798.
Perimeter Road "B" has a 60-foot (18-m) offset (distance from the barrier to the restricting opposite
curb). Using Table 1 in Section 6, a vehicle traveling at 50 mph (80 kph) can safely turn on a
maximum 167-foot (51 m) radius curve without skidding. At this speed and angle of approach to
the barrier, the vehicle will strike the barrier at an angle. Because the amount of speed directed at
the barrier is related to the angle of impact (Table 1), the speed directed at the barrier is 76.6 percent
of the 50-mph (80-kph) speed, or 38 mph (61 m). Using Table 2 in Section 6 and rounding up to
the next highest speed [40 mph (64 kph)], the kinetic energy transferred to the barrier will be
214,000 ft-lbf (29 kgf-m), if the threat is a 4,000-pound (1,818-kg) vehicle, and 802,000 ft-lbf (111
kgf-m), if the threat is a 15,000-pound (6,818-kg) vehicle.
Once the kinetic energy has been calculated, refer to Appendix E for a listing of passive
barriers and penetration distances that can be used to select the most effective barrier. Anchored
Jersey Barriers could be used for the low-level threat of a 4,000-pound (1,818-kg) vehicle, and a
bollard system or concrete planter would be the only passive barriers that would be capable of
stopping a 15,000-pound (6,818-kg) vehicle. For the larger threat, it would be appropriate to install
concrete blocks, as shown in Figure 32 in Section 8, and space them in accordance with the
information from Table 14 to reduce the vehicle speed to 30 mph (48 kph) or less.