Geometric Design - Horizontal Curves

Question 1

What does ideal alignment follow?

Answer 1

Natural terrain of countryside

Question 2

Influence of terrain

Answer 2

Level - grading not major cost

Rolling - grading and curvature important

Mountainous - grading is main issue

Question 3

Physical location of roadway developed with respect to what?

Answer 3

Calculated centerline

Question 4

Horizontal alignment consists of: (4)

Answer 4

Bearings
Curvature
Transitions
Superelevation

Question 5

What is superelevation?

Answer 5

The amount by which the outer edge of a curve on the road is banked above the inner edge.

Question 6

Why is superelevation important?

Answer 6

Provides safety and comfort

Question 7

Normal crown is typically determined by what?

Answer 7

Drainage (2% recommended)

Question 8

Limiting factors for superelevation

Answer 8

Climate
Constructability
Adjacent land use
Frequency of slow moving vehicles
High center of gravity
Urban/High volume

Question 9

Forces in superelevation

Answer 9

Centrifugal force
Side friction
Roll angle

Question 10

Side friction factor depends on:

Answer 10

Speed of vehicle
Type and condition of road
Type and condition of tires

Question 11

Vertical alignment - cut/fill…what is ideal?

Answer 11

cut balanced with fill

Question 12

Ideal grades?

Answer 12

Long distance between points of intersection, long curves between tangents. This provides smooth riding quality and good visibility

Question 13

Why ideal grade not always possible?

Answer 13

Inhibited by:
Existing land use
Soil types
Adjacent features (streams, RR)

Question 14

Minimum grade for highway

Answer 14

0.5%