Lecture 6, Tues FEb20 You were absent// lecture 6 on moodle all

Question 1

Types of horizental curves (4types)

Answer 1

Simple curves:
– With single constant radius
Reverse curves
_Two consecutive curves that
turn in opposite directions
Compound curves:
– Two or more simple curves of
different radii in succession
Spiral curves (or transition curves)
_Curves with a continuously changing radius from inf at
tangent to R at curve (At start of transition curve it will be inf then it will change to R) (Look at pictures page 8)

Question 2

There are two functions of spiral curves

Answer 2

1-they provide a transition and reduce sudden change in curvature at junction of tangent
and circular curve
2-Provide a rational basis for superelevation transition.

Question 3

Memorize page 9 it has all the definitions

Answer 3

True

Question 4

`Notes on the horizental curve

Answer 4

Horizontal curve stationing, curve length, and
curve radius are usually measured to the
centerline of the road meaning that if we have 4 lane highway, the centerline is the live seperating the going traffic from the coming traffic

Radius determined based on centripetal and
centrifugal forces is measured from the
innermost vehicle path (assumed to be the
midpoint of the innermost vehicle lane)

Usually delta (the central angle) and the station of the PI
are known

Curve selection:
– Any two given tangents can be connected by many circulararcs
– We can assume one of the following quantities:
• R usual to assume
• T, E possible to assume
• L unusual to assume
– Assuming one quantity ⇒ others are computed based on derived relations
– E.g. to provide for a certain design speed, may require R > Rmin; or field conditions may dictate a certain controlling quantity

Question 5

Example 10 solve (page 16)

Answer 5

True

Question 6

Stopping Sight distance and horizental curves

Answer 6

Sight distance is measured along centerline of travel lane (not center line of the road)
For a certain SSD, a clearance Ms must be provided (Look at page 21 you will find everything.)

Question 7

SSD equation of the horizental curves

Answer 7

Look at page 22

Question 8

Page 23 example 11 solve

Answer 8

True

Question 9

Exercise session page 28 all

Answer 9

True