Horizontal Alignment Of Highways

Question 1

corresponds roughly
to x and z coordinates

Answer 1

horizontal alignment (plan view)

Question 2

corresponds to highway length (measured along some constant elevation) and y coordinates (elevation)

Answer 2

vertical alignment (profile view)

Question 3

types of horizontal curves

Answer 3

1. Circular curve
2. Simple curve
3. Compound Curve
4. Reverse Curve
5. Broken Back Curve
6. transitional curve or Easement Curve

Question 4

Sharpness of curve can be expressed by using two measurements:

Answer 4

a. Radius, R
b. Degree of curvature, D°

Question 5

types of reverse curve

Answer 5

-with parallel tangents
-with non parallel tangents

Question 6

types of transitional curve

Answer 6

• Clothoid
• symmetrical clothoid

Question 7

For large radius (as in railroad practice), distances along the arc
are considered to be the same as along the chords.

Answer 7

Circular Curve

Question 8

definition being followed in highway practice

Answer 8

arc definition

Question 9

definition used for railroad practice

Answer 9

chord definition

Question 10

Stationing In metric system, the length l used is ___ m for both arc and chord definitions. In English system, the length l used is ____ ft for both arc and chord definitions.

Answer 10

a. 20
b. 100

Question 11

defined as a circular arc between two tangents.

Answer 11

Simple curve

Question 12

point of intersection of two
tangents

Answer 12

PI

Question 13

point of curvature or beginning of curve

Answer 13

PC

Question 14

point of tangency or end of curve

Answer 14

PT

Question 15

external angle of deflection between tangents

Answer 15

Δ

Question 16

tangent distance

Answer 16

T

Question 17

long chord connecting PC and PT

Answer 17

Lc

Question 18

external distance

Answer 18

E

Question 19

middle ordinate

Answer 19

M

Question 20

length of curve from PC to PT R:
radius of curve

Answer 20

L

Question 21

a two-arc simple curve having its centers on the same side of the common tangent.

Answer 21

Compound Curve

Question 22

a two-arc simple curve having its centers on opposite sides. This type of curve is usually inadmissible on high-speed routes because superelevation at the point of reversal cannot be provided.

Answer 22

Reverse Curve

Question 23

characterized by a short tangent
between two curves in the same direction. This type of curve should be avoided in design since most drivers do not expect succeeding curves to be in the same direction.

Answer 23

Broken Back Curve

Question 24

a spiral that serves as a transition path as the vehicle enters or leaves a circular curve. This type of curve follows a natural path as the driver turns the steering wheel

Answer 24

transitional curve or Easement Curve

Question 25

most well-known transition curve

Answer 25

Clothoid

Question 26

T or F
clothoid enables a car driver to ride smoothly by turning the
steering wheel with a constant speed, defining a clothoidal spiral, a continuous and linear curvature variation.

Answer 26

True

Question 26

a circular curve having two clothoids at each end serving as transition paths. The two clothoids have exactly the same properties.

Answer 26

symmetrical clothoid

Question 27

3 Standard for the length of clothoid

Answer 27

1. Based on travel time
2. Based on rate of change of acceleration, p
3. Based on aesthetics