MODULE 1 UNIT 2: Design Requirements

Question 1

DESIGN CONTROLS

Answer 1

Vehicles, Traffic, Road users

Question 2

DESIGN REQUIREMENTS FOR HIGHWAYS

Answer 2

1. DESIGN SPEED
2. SIGHT DISTANCES
3. MINIMUM RADIUS OF CURVATURE
4. SUPERELEVATION
5. DESIGN VOLUME
6. NUMBER OF LANES

Question 3

• the maximum safe speed that can be maintained over a specified section of a highway, given that the conditions are favorable
  – the basis of all other elements of the highway
  – designs speeds are designated for different types of roadways

Answer 3

DESIGN SPEED

Question 4

true or false:
Design speeds must be maintained for the entirety of the highway

Answer 4

true

Question 5

true or false:
if terrain condition or some obstructions would not allow this, the design speed may be reduced by 10 – 20 kph at adjacent sections**

Answer 5

true

Question 6

The length of the road that is highly visible to the driver even from a distance ahead

Answer 6

SIGHT DISTANCE

Question 7

– The actual distance observed along the road surface which is visible from a specified height above the carriage way
– This distance lets the driver see all stationary and moving objects in front of the vehicle

Answer 7

SIGHT DISTANCE AT A POINT

Question 8

5 TYPES OF SIGHT DISTANCES

Answer 8

Stopping Sight Distance (SSD)
Passing Sight Distance (PSD)
Intermediate Sight Distance (ISD)
Head Light Sight Distance
Sight Distance @ intersections

Question 9

Minimum safe distance required to stop to avoid collision

Answer 9

Stopping Sight Distance (SSD)

Question 10

Minimum safe distance required to safely pull out of a traffic lane and pass a vehicle in the same direction

Answer 10

Passing Sight Distance (PSD)

Question 11

twice the value of the SSD

Answer 11

Intermediate Sight Distance (ISD)

Question 12

the distance available for the driver during night travel

Answer 12

Head Light Sight Distance

Question 13

distance available to enter an intersection

Answer 13

Sight Distance @ intersections

Question 14

Also known as Absolute Minimum Sight Distance

Answer 14

STOPPING SIGHT DISTANCE (SSD)

Question 15

• The minimum distance open to the vision of the driver intended to stop the vehicle to avoid collision with an obstruction on the carriage way
• minimum value normally computed for wet pavement condition
• Affected by the driver’s reaction time

Answer 15

STOPPING SIGHT DISTANCE (SSD)

Question 16

• the distance travelled by vehicle during total reaction time of driver
• lag distance

Answer 16

L1

Question 17

• the distance travelled by the vehicle after the application of brakes
• braking distance

Answer 17

L2

Question 18

coefficient of longitudinal friction

Answer 18

f

Question 19

range of f

Answer 19

0.29 to 0.40

Question 20

AASHTO:
Reaction time: ___

Answer 20

2.5 seconds

Question 21

AASHTO:
Perception time: _____

Answer 21

1.5 seconds

Question 22

Velocity Equation:

Answer 22

Speed = Distance / time

Question 23

formula of Reaction time, t

Answer 23

tp + tb

Question 24

perception time

Answer 24

tp

Question 25

brake time

Answer 25

tb

Question 26

- also known as overtaking sight distance (OSD) - the minimum distance open to sight of driver intending to overtake a vehicle safely without causing collision with the opposite vehicle

Answer 26

PASSING SIGHT DISTANCE

Question 27

at curves, this length must be visibly free of obstructions in order to permit a moving vehicle at design speed to pass a slower moving vehicle

Answer 27

PASSING SIGHT DISTANCE

Question 28

Factors affecting Overtaking Sight Distance

Answer 28

1. Speed of overtaking vehicle (V, m/s) 2. Speed of overtaken vehicle (Vb, m/s) 3. Speed of opposite vehicle (Vo, m/s) 4. Reaction time of overtaking vehicle driver 5. Spacing between the vehicles (S) 6. Acceleration of overtaking vehicle (m/s2) 7. Gradient of the road

Question 29

for 2-lane highways, it is the shortest distance required for a vehicle to safely maneuver out of the traffic lane, overtake and return to its lane without interfering the passed vehicle or the opposing lane

Answer 29

PASSING SIGHT DISTANCE

Question 30

distance moved during reaction time and initial acceleration just before changing lanes

Answer 30

d1

Question 31

distance traveled during overtaking (at the left/opposite lane)

Answer 31

d2

Question 32

distance between the passing vehicle at the end of maneuvre and the opposing vehicle

Answer 32

d3

Question 33

distance traversed by an opposing vehicle for two-thirds of the time the passing vehicle occupies the left lane

Answer 33

d4