lecture 13

Question 1

What are traffic control devices there is a picture before see it

Answer 1

devices used to promote safety and efficiency by regulating movements of all road users

Question 2

What are the five basic requirements for the traffic control devices to be effective

Answer 2

#convey a clear simple meaning
# Give adequate time for proper response
#Command respect from road users
#command attention
#fulfill a need

Question 3

What is the function of signs in traffic control devices

Answer 3

Signs convey information through their shape , color, message and placement

Question 4

what are the basic elements or factors in an intersection design

Answer 4

# human factor (like driving habits and perception reaction time)
#Traffic considerations ( vehicle speeds and public transport services)
#physical elements or factors ( sight distance and vertical alignment of the intersection)
#Economic factors (cost and energy consumptions)

Question 5

There is a difference between physical intersection area which is only related to the geometry and functional intersection area which is more related to the function also

Answer 5

see picture page 16

Question 6

Intersection sight distance

Answer 6

sight distance that must be provided at the intersection

Question 7

purpose of intersection sight distance

Answer 7

it is to provide sight distance at the intersections to allow drivers to perceive the presence of potentially conflicting vehicles and traffic control devices

Question 8

How do we provide intersection sight distance

Answer 8

by clearing specified areas along the intersection corners and legs from obstructions

Question 9

There are two types of clear sight triangles in intersection sight distance

Answer 9

#Approach sight triangle (uncontrolled or yield controlled see page 20)
#Departure sight triangle (stop controlled see page 21, the triangles are smaller)

Question 10

Types and examples of intersections

Answer 10

see page 24-25-26-27

Question 11

Why do we use intersection channelization and how it is done

Answer 11

We use intersection channelization in order to separate turn lanes from through lanes , channelization is done through solid white lines or through raised barriers

Question 12

What is the purpose of intersection channelization

Answer 12

#direct traffic movements
#provide refuge for crossing vehicles and pedestrians
# prevent prohibited  turns
# establish speed control over vehicles entering an intersection

Question 13

Page 30-31-32-33

Answer 13

must study

Question 14

Rotary intersection (round about) definition and properties

Answer 14

A roundabout consists of one-way road around a central island where all traffic approaching the intersection merges into this one way road. All the movements happens with weaving and without crossing.

Question 15

Advantages of rotary intersections

Answer 15

#at low volumes it reduces delay by replacing direct crossings of vehicles by weaving
#when there are more than 4 intersections involved, rotaries provide simplified design

Question 16

Disadvantages of rotary intresections

Answer 16

#require large area for design
#less suitable in areas with high pedestrian traffic
# functions properly at low speeds and volumes

Question 17

Picture page 37

Answer 17

must study

Question 18

What are safety benefits of round abouts

Answer 18

#produces low speed environment
#eliminates opposing traffic
#Reduce speed differential among conflicting movements
#reduce severity and frequency of collisiion

Question 19

rotary with flyover

Answer 19

pic page 39 study

Question 20

How is the overall intersection assessment is done

Answer 20

# by assessing delay per vehicle
# by assessing safety ( crashes severity)
# convenience to all users ( pedestrian, byciclists, people with disabilities, and elderly people)

Question 21

Freeway entrances and exits

Answer 21

Freeway entrance : on ramp

Freeway exits : off ramp

Question 22

Ramps that lead to/from loops or local roads are not designed at the same speed as the expressway

Answer 22

true

Question 23

how we design freeway entrances and exits

Answer 23

we design ramps entrances and exits by providing sufficient length to allow vehicles to accelerate or decelerate so that they can merge with the freeway or away from it

Question 24

what are the two possible designs of the on-ramps

Answer 24

#taper design: blending into "through lane"
#parallel design:"auxiliary lane" parallel to "through lane"
See pic page 47

Question 25

How L (length) is measured in on-ramps

Answer 25

L is measured starting from the point vehicle enters a path parallel to outer lane and ending at a location where acceleration lane drops below 12 ft.

Question 26

Off ramps properties

Answer 26

# vehicles leaving freeway need a distance to decelerate away from stream of the on-going traffic
# it is achieved by taper or parallel lane
# we also want to find L
# see pic from page 50 till 52