lecture 9

Question 1

Cross section

Answer 1

meaning when we have cross-section view of the road

Question 2

We have principal cross section elements like

Answer 2

Travel lanes
shoulders
medians

Question 3

ask about :We have secondary elements such as

Answer 3

ask about :Median barrier (guard rails)
roadside barriers
curbs
sidewalk
cross-slopes
side slopes 
drainage channel
right of way

Question 4

Road way

Answer 4

portion of highway including shoulders without median for vehicular use
A divided highway has two or more roadways

Question 5

Traveled way

Answer 5

the portion of roadway for the movement of vehicles , exclusive of shoulders

Question 6

page 6 lecture 9

Answer 6

Draw it and memorise it

Question 7

page 9 and 10

Answer 7

also draw and memorise it

Question 8

What is a shoulder

Answer 8

A shoulder is the portion of ““roadway””” tht is adjacent with the traveled lane that is needed for capacity and safety reasons

Question 9

Shoulders Safety advantages (4 is enough)

Answer 9

#Vehicles can stop because of mechanical difficulties and emergencies.
#motorists can stop to consult  road maps
# evasive maneuvers to avoid potential crashes and reduce their sverity
#Discharge for storm water from travel lanes which reduce splashes
# increased sight distance for vehicles entering the roadway
#recovery area to regain control of a vehicle

Question 10

Shoulders Capacity advantages

Answer 10

# Provide greater effective turning radii for trucks
# Provided space for pedestrian and bicycle use
# Provided space for bus stops
# Provided space for occasional encroachment of vehicles
# Provided space for mail delivery trucks
# provided space for detouring traffic during construction

Question 11

Shoulders maintenance advantage

Answer 11

# snow removal and storage
# clearance is provided for signs and guardrails
# clearance is provided for portable maintenance  signs.

Question 12

Shoulders dimensions

Answer 12

#Minimum width = 0.6 m (for difficult terrain and low volume highways)
# On rural collectors : shoulder width = 1.8 - 2.4 m
# On highway with heavy traffic : shoulder width = 3.6 m

Question 13

Shoulders characteristic

Answer 13

# should be contrasting with travel lanes in color or texture
# Can have a median shoulder for divided highwat

Question 14

Median, what are

Answer 14

Section of divided highway which separates lanes in opposing directions

Question 15

Median functions

Answer 15

#Stopping during emergency
#Refugee for pedestrians
#Storage for left turning and U turning vehicles

Question 16

Medians types (Medians can be)

Answer 16

#Raised (urban arterials)
#Flush/Striped
#Depressed(free way)

Question 17

Medians dimensions

Answer 17

#Width vary between 0.6 and 24 meters including median shoulders.
# AASHTOO recommends a minimum of 3m for 4 lanes urban free way
#Paint-striped median is between 0.6 and 1.2 m.

Question 18

Frontage roads or what is known as service roads.
// Functions:

Answer 18

# Control access to arterials
# Segregate loacl trafffic fro the higher speed through-traffic
#Used on all types of highways
# Provide more favorable access for commercial and residential development than the faster moving arterial street and helps preserve the safety and capacity of the arterial.

Question 19

Secondary elements:

Roadside and median barriers function

Answer 19

Prevent vehicles that left the traveled way from hitting an object that has greater crash severity potential than the barrier itself
-Roadside barrier: protect vehicles from roadside hazards
Median barrier: prevent crossing from one side to another.

Question 20

Secondary elements:

Typical roadside barriers

Answer 20

guardrails

Crash cushions

Question 21

Secondary elements:
roadside barriers
Guardrails

Answer 21

Longitudinal barriers to prevent vehicles from leaving roads

Question 22

Secondary elements:
roadside barriers
Typical location of guardrails

Answer 22

# Outside of sharp edges
# At section with high fills

Question 23

Secondary elements:
roadside barriers
Crash Cushions function

Answer 23

decelerate errant vehicles to a stop

Question 24

Secondary elements:

Median barriers

Answer 24

Concrete - W section.

Question 25

Secondary elements: | Curbs

Answer 25

Raised structures made of cement used mainly on urban highways not to be used on high-speed highway.

Question 26

Secondary elements: | Curbs purposes

Answer 26

``` # roadway edge delineation # discouraging vehicles from leaving the roadway #Delineation of pedestrian walkways and protection of pedestrians #Minimizing collision between vehicles and structures #Control of drainage #Discourage cars from driving close to the wall. ```

Question 27

Secondary elements: | Sidewalks

Answer 27

``` #Usually in urban areas only. #Minimum width of 1.2 m in residential areas. #Minimum width 1.2-2.4 m or more in commercial areas #Proper attention should be given to the needs of persons with disabilities whose means of mobility are dependent upon wheelchairs and other devices ( for example we can provide curb ramps in sidewalks.) ```

Question 28

Secondary elements: Cross slopes (Highway without median) see pics

Answer 28

Pavement is sloped from the middle downwards to both sides of the highway implies rounded crown cross slopes.

Question 29

Secondary elements: Cross slopes (Highway with median) see pics

Answer 29

``` #Each roadway is crowned in each direction of travel ( Here surface water is drained quickly away but requires more drainage facilities, it is preferred for areas with heavy rain.) # Slope whole pavement in one direction ```

Question 30

Secondary elements: Cross Slopes Each roadway is crowned separately see pics

Answer 30

Advantages #Rapidly draining the pavement during rainstorm. #Difference between high and low points in the cross section is minimal Disadvantages #More underground drainage lines and inlets are needed. # Treatment of intersections is more difficult because of the number of high and low points on the cross section

Question 31

Secondary elements: Cross Slopes Roadways with unidirectional cross slopes see pics

Answer 31

``` advantages # provide more comfort to drivers when they change lanes # more economical, provide more savings in drainage structures and minimize drainage across the inner, and simplify treatment of intersecting streets # Outer lanes which are used by most traffic are more free of surface water ```

Question 32

Rates of cross slopes

Answer 32

AASHTO recommends 1.5% - 2% | Shoulder cross slope: 2- 6% to provide adequate drainage.

Question 33

Secondary elements: | Side Slopes

Answer 33

``` #It provides stability of earthworks # Gradient of side slope= 1V:3H or flatter #In cases of high cut or fill we can use 1V:3H # Retaining wall may be utilized for steeper slopes ```

Question 34

Secondary elements: | Right of way

Answer 34

``` #The ROW is the total land area to be acquired for constructing the road and all its elements ```

Question 35

Secondary elements: | Right of way width

Answer 35

#The width should accommodate the following: – All elements of highway cross-section – Public utility facilities along highway – Any planned widening #If 2-lane urban collector: 12-18 m #If 4-lane arterial (2 lanes in each direction): 25 m (desirable)