Question

UI LIL 111111Wuy. 5. An elevated expressway goes through an urban area, and crosses a local street as shown in Figure 3.10. The partial cloverleaf exit ramp is on a 2% downgrade and all vehicles leaving the expressway must stop at the intersection with Local Street. Determine minimum ramp radius and length of ramp for the following conditions: Maximum speed on expressway is 60 mph. Distance between exit signs and exit ramp is 260 ft. Letter head on road sign is 3 inches and can be viewed by the design driver at 150 ft away from the sign. PRT is 2.5 sec, f=0.3, the central angle of the ramp is 90 degree. Assume sufficient superelevation is provided. 260 - Expressway Excit sign Stop sign Figure 3.10 Layout of Elevated Expressway Ramo, and Local Street for Problem 3-15

Answer 1

Solution! - inces of Reliability = (letter height) xgott for each leherheight = 31x550' = 150ft Relia biury dill SSD = 1.97:07 + .. . Vit - 300 + 0) Givens G=6 Reliability dista 150ft: SSD = 260++, u,= 60 milh. it = 2.5 sec a = 11.2 ft/sec G = 32.2 ft/sec² 60-- U - 150 260 = (1.47 x60x 2.5)4 : 301132, 10) 260 = 220.5+ GOPW-150 : 10.434 = 46.281 milh 2 : 16 22.60 . Måninum radius veq for this extra O, A R . . fi coeft 15(e+fs) of slide friction =0.12, (from table) ...620.org for Gomilh R = (40.28132 15(0.08 + 0.12) IR 540.45 ofty

The length required for this. ramis. SSD = 147 utt - Uz 2 30 ( VU,2 1 G) 550 = (1,47 x 40.281% 25) of 40.2812 30(11? - 1 32.2. SSD: 313.01ft,