Superelevation Transitions Quiz 5

What is the percentage elevation for the normal crown?

2%

What is the purpose of a horizontal curve superelevation transition?

Provide a gradual transition from normal cross slope to full superelevation on the HC, without appreciable reduction in speed while ensuring safety and comfort

What is superelevation transition?

The length over which the change from normal crossfall to full superelevation takes place.

What is the “2/3 - 1/3” rule?

Caltrans practice that requires 2/3 of the superelevation runoff lenngth be tangent before the PC, and 1/3 after.

What is the Normal Crown?

Standard cross-slope on a straight section of road where the center is the highest point.

What is the crown runoff?

length where the cross-slope transitions from a normal crown to a flat crown

What is the superelevation runoff?

Distance required to transition from a flat (0%) cross-slope to full superelevation

Given a “superelevation runoff” length of 180 ft. Using the “2/3 -1/3” rule, how far from the beginning of full superelevation is the station of the PC?

60 ft

In the region of the “normal crown”, is the elevation of the outside lane edge of pavement greater than, less than, or the same as the centerline of the road?

less than

Given a lane width and superelevation rate (e), how can you determine the offset of the inside lane edge of pavement from the centerline elevation of the road at full superelevation?

multiply lane width by superelevation rate

Should VCs be within HCs or HCs withing VCs>

Keep VCs within HCs

Is it a good idea to have a horizontal curve starting immediately after the high point of a crest vertical curve?

Not a good idea. Keep VCs within HCs

Is it considered good highway design practice to start a small-radius horizontal curve near the low point of a sag vertical curve?

Not good highway design practice. Keep VCs within HCs