Chapter 23 - Multilane Highways Notes | EduRev

: Chapter 23 - Multilane Highways Notes | EduRev

 Page 1


Transportation Systems Engineering 23. Multilane Highways
Chapter 23
Multilane Highways
23.1 Introduction
Increasing tra?c ?ow has forced engineers to increase the number of lanes of highways in order
to provide good manoeuvring facilities to the users. The main objectives of this lecture is to
analyze LOS which is very importantfactorforatra?c engineer because it describes the tra?c
operational conditions within a tra?c stream. Also we are going to study the characteristics
and capacity for multilane highways. Free-?ow speed is an important parameter that is being
used extensively for capacity and level-of- service analysis of various types of highway facilities.
23.2 Multilane Highways
A highway is a public road especially a major road connecting two or more destinations. A
highway with at least two lanes forthe exclusive use of tra?c in each direction, with no control
or partial control of access, but that may have periodic interruptions to ?ow at signalized
intersections not closer than 3.0 km is called as multilane highway. They are typically located
in suburban areas leading to central cities or along high-volume rural corridors that connect
two cities or important activity centers that generate a considerable number of daily trips.
23.2.1 Highway Classi?cation
There are various ways of classi?cation of highways; we will see classi?cation of highways
according to number of lanes.
• Two lane highways.
• Multilane highways
Dr. Tom V. Mathew, IIT Bombay 23.1 February 19, 2014
Page 2


Transportation Systems Engineering 23. Multilane Highways
Chapter 23
Multilane Highways
23.1 Introduction
Increasing tra?c ?ow has forced engineers to increase the number of lanes of highways in order
to provide good manoeuvring facilities to the users. The main objectives of this lecture is to
analyze LOS which is very importantfactorforatra?c engineer because it describes the tra?c
operational conditions within a tra?c stream. Also we are going to study the characteristics
and capacity for multilane highways. Free-?ow speed is an important parameter that is being
used extensively for capacity and level-of- service analysis of various types of highway facilities.
23.2 Multilane Highways
A highway is a public road especially a major road connecting two or more destinations. A
highway with at least two lanes forthe exclusive use of tra?c in each direction, with no control
or partial control of access, but that may have periodic interruptions to ?ow at signalized
intersections not closer than 3.0 km is called as multilane highway. They are typically located
in suburban areas leading to central cities or along high-volume rural corridors that connect
two cities or important activity centers that generate a considerable number of daily trips.
23.2.1 Highway Classi?cation
There are various ways of classi?cation of highways; we will see classi?cation of highways
according to number of lanes.
• Two lane highways.
• Multilane highways
Dr. Tom V. Mathew, IIT Bombay 23.1 February 19, 2014
Transportation Systems Engineering 23. Multilane Highways
                                                    Figure 23:1: Divided multilane highway in a rural/suburban environment
Figure 23:2: Undivided multilane highway in a rural/suburban environment
23.2.2 Highway Characteristics
Multilane highways generally have posted speed limits between 60 km/h and 90 km/h. They
usuallyhavefourorsixlanes,oftenwithphysicalmediansortwo-wayrightturnlanes(TWRTL),
although they may also be undivided. The tra?c volumes generally varies from 15,000- 40,000
vehicles per day. It may also go up to 100,000 vehicles per day with grade separations and no
cross-median access. Tra?c signals at major intersections are possible for multilane highways
which facilitate partial control of access. Typical illustrations of multilane highway con?gura-
tions are provided in Fig. 23:1 and 23:2
23.3 Highway Capacity
Animportantoperationcharacteristicofanytransportfacilityincludingthemultilanehighways
is the concept of capacity. Capacity may be de?ned as the maximum sustainable ?ow rate at
which vehicles or persons reasonably can be expected to traverse a point or uniform segment of
Dr. Tom V. Mathew, IIT Bombay 23.2 February 19, 2014
Page 3


Transportation Systems Engineering 23. Multilane Highways
Chapter 23
Multilane Highways
23.1 Introduction
Increasing tra?c ?ow has forced engineers to increase the number of lanes of highways in order
to provide good manoeuvring facilities to the users. The main objectives of this lecture is to
analyze LOS which is very importantfactorforatra?c engineer because it describes the tra?c
operational conditions within a tra?c stream. Also we are going to study the characteristics
and capacity for multilane highways. Free-?ow speed is an important parameter that is being
used extensively for capacity and level-of- service analysis of various types of highway facilities.
23.2 Multilane Highways
A highway is a public road especially a major road connecting two or more destinations. A
highway with at least two lanes forthe exclusive use of tra?c in each direction, with no control
or partial control of access, but that may have periodic interruptions to ?ow at signalized
intersections not closer than 3.0 km is called as multilane highway. They are typically located
in suburban areas leading to central cities or along high-volume rural corridors that connect
two cities or important activity centers that generate a considerable number of daily trips.
23.2.1 Highway Classi?cation
There are various ways of classi?cation of highways; we will see classi?cation of highways
according to number of lanes.
• Two lane highways.
• Multilane highways
Dr. Tom V. Mathew, IIT Bombay 23.1 February 19, 2014
Transportation Systems Engineering 23. Multilane Highways
                                                    Figure 23:1: Divided multilane highway in a rural/suburban environment
Figure 23:2: Undivided multilane highway in a rural/suburban environment
23.2.2 Highway Characteristics
Multilane highways generally have posted speed limits between 60 km/h and 90 km/h. They
usuallyhavefourorsixlanes,oftenwithphysicalmediansortwo-wayrightturnlanes(TWRTL),
although they may also be undivided. The tra?c volumes generally varies from 15,000- 40,000
vehicles per day. It may also go up to 100,000 vehicles per day with grade separations and no
cross-median access. Tra?c signals at major intersections are possible for multilane highways
which facilitate partial control of access. Typical illustrations of multilane highway con?gura-
tions are provided in Fig. 23:1 and 23:2
23.3 Highway Capacity
Animportantoperationcharacteristicofanytransportfacilityincludingthemultilanehighways
is the concept of capacity. Capacity may be de?ned as the maximum sustainable ?ow rate at
which vehicles or persons reasonably can be expected to traverse a point or uniform segment of
Dr. Tom V. Mathew, IIT Bombay 23.2 February 19, 2014
Transportation Systems Engineering 23. Multilane Highways
Table 23:1: Free ?ow speed and capacity for Multilane highway
Types of facility Free ?ow Capacity
speed(kmph) (pcphpl)
Multilane 100 2200
90 2100
80 2000
70 1900
a lane or roadway during a speci?ed time period under given roadway, tra?c, environmental,
and control conditions; usually expressed as vehicles per hour, passenger cars per hour, or
persons per hour. There are two types of capacity, possible capacity and practical capacity.
Possible capacity is de?ned as the maximum number of vehicles that can pass a point in one
hour under prevailing roadway and tra?c condition. Practical capacity on the other hand is
the maximum number that can pass the point without unreasonable delay restriction to the
average driver’s freedom to pass other vehicles. Procedure for computing practical capacity for
the uninterrupted ?ow condition is as follows:
1. Select an operating speed which is acceptable for the class of highways the terrain and
the driver.
2. Determine the appropriate capacity for ideal conditions from table 1.
3. Determine the reduction factor for conditions which reduce capacity (such as width of
road, alignment, sight distance, heavy vehicle adjustment factor).
4. Multiply these factors by ideal capacity value obtained from step 2.
23.4 Level of Service
Level of service (LOS) is a qualitative term describing the operational performance of any
transportation facility. The qualitative performance measure can be de?ned using various
quantitative terms like:
1. Volume to capacity ratio,
2. Mean passenger car speed,( in km/h)
Dr. Tom V. Mathew, IIT Bombay 23.3 February 19, 2014
Page 4


Transportation Systems Engineering 23. Multilane Highways
Chapter 23
Multilane Highways
23.1 Introduction
Increasing tra?c ?ow has forced engineers to increase the number of lanes of highways in order
to provide good manoeuvring facilities to the users. The main objectives of this lecture is to
analyze LOS which is very importantfactorforatra?c engineer because it describes the tra?c
operational conditions within a tra?c stream. Also we are going to study the characteristics
and capacity for multilane highways. Free-?ow speed is an important parameter that is being
used extensively for capacity and level-of- service analysis of various types of highway facilities.
23.2 Multilane Highways
A highway is a public road especially a major road connecting two or more destinations. A
highway with at least two lanes forthe exclusive use of tra?c in each direction, with no control
or partial control of access, but that may have periodic interruptions to ?ow at signalized
intersections not closer than 3.0 km is called as multilane highway. They are typically located
in suburban areas leading to central cities or along high-volume rural corridors that connect
two cities or important activity centers that generate a considerable number of daily trips.
23.2.1 Highway Classi?cation
There are various ways of classi?cation of highways; we will see classi?cation of highways
according to number of lanes.
• Two lane highways.
• Multilane highways
Dr. Tom V. Mathew, IIT Bombay 23.1 February 19, 2014
Transportation Systems Engineering 23. Multilane Highways
                                                    Figure 23:1: Divided multilane highway in a rural/suburban environment
Figure 23:2: Undivided multilane highway in a rural/suburban environment
23.2.2 Highway Characteristics
Multilane highways generally have posted speed limits between 60 km/h and 90 km/h. They
usuallyhavefourorsixlanes,oftenwithphysicalmediansortwo-wayrightturnlanes(TWRTL),
although they may also be undivided. The tra?c volumes generally varies from 15,000- 40,000
vehicles per day. It may also go up to 100,000 vehicles per day with grade separations and no
cross-median access. Tra?c signals at major intersections are possible for multilane highways
which facilitate partial control of access. Typical illustrations of multilane highway con?gura-
tions are provided in Fig. 23:1 and 23:2
23.3 Highway Capacity
Animportantoperationcharacteristicofanytransportfacilityincludingthemultilanehighways
is the concept of capacity. Capacity may be de?ned as the maximum sustainable ?ow rate at
which vehicles or persons reasonably can be expected to traverse a point or uniform segment of
Dr. Tom V. Mathew, IIT Bombay 23.2 February 19, 2014
Transportation Systems Engineering 23. Multilane Highways
Table 23:1: Free ?ow speed and capacity for Multilane highway
Types of facility Free ?ow Capacity
speed(kmph) (pcphpl)
Multilane 100 2200
90 2100
80 2000
70 1900
a lane or roadway during a speci?ed time period under given roadway, tra?c, environmental,
and control conditions; usually expressed as vehicles per hour, passenger cars per hour, or
persons per hour. There are two types of capacity, possible capacity and practical capacity.
Possible capacity is de?ned as the maximum number of vehicles that can pass a point in one
hour under prevailing roadway and tra?c condition. Practical capacity on the other hand is
the maximum number that can pass the point without unreasonable delay restriction to the
average driver’s freedom to pass other vehicles. Procedure for computing practical capacity for
the uninterrupted ?ow condition is as follows:
1. Select an operating speed which is acceptable for the class of highways the terrain and
the driver.
2. Determine the appropriate capacity for ideal conditions from table 1.
3. Determine the reduction factor for conditions which reduce capacity (such as width of
road, alignment, sight distance, heavy vehicle adjustment factor).
4. Multiply these factors by ideal capacity value obtained from step 2.
23.4 Level of Service
Level of service (LOS) is a qualitative term describing the operational performance of any
transportation facility. The qualitative performance measure can be de?ned using various
quantitative terms like:
1. Volume to capacity ratio,
2. Mean passenger car speed,( in km/h)
Dr. Tom V. Mathew, IIT Bombay 23.3 February 19, 2014
Transportation Systems Engineering 23. Multilane Highways
Figure 23:3: LOS A
3. Density, (in p/kmln).
Basically any two of the following three performance characteristics can describe the LOS for a
multilane highway. Each of these measures can indicate how well the highway accommodates
thetra?cdemandsincespeeddoesnotvaryoverawiderangeof?ows, itisnotagoodindicator
ofservice quality. Densitywhich isameasureofproximity ofothervehicles inthetra?cstream
and is directly perceived by drivers and does not vary with all ?ow levels and therefore density
is the most important performance measure for estimating LOS. Based on the quantitative
parameter, the LOS of a facility can be divided into six qualitative categories, designated as
LOS A,B,C,D,E,F The de?nition of each level of service, is given below:
23.4.1 Level of Service A
Travel conditions are completely free ?ow. The only constraint on the operation of vehicles
lies in the geometric features of the roadway and individual driver preferences. Lane changing,
merging and diverging manoeuvre within the tra?c stream is good, and minor disruptions to
tra?c are easily absorbed without an e?ect on travel speed. Average spacing between vehicles
is a minimum of 150 m or 24 car lengths. Fig. 23:3 shows LOS A.
23.4.2 Level of Service B
Travel conditions are at free ?ow. The presence of other vehicles is noticed but it is not a con-
straint on the operation of vehicles as are the geometric features of the roadway and individual
driver preferences. Minor disruptions are easily absorbed, although localized reduction in LOS
arenoted. Average spacing between vehicles isaminimum of150mor24carlengths. Fig.23:4
below shows LOS B.
Dr. Tom V. Mathew, IIT Bombay 23.4 February 19, 2014
Page 5


Transportation Systems Engineering 23. Multilane Highways
Chapter 23
Multilane Highways
23.1 Introduction
Increasing tra?c ?ow has forced engineers to increase the number of lanes of highways in order
to provide good manoeuvring facilities to the users. The main objectives of this lecture is to
analyze LOS which is very importantfactorforatra?c engineer because it describes the tra?c
operational conditions within a tra?c stream. Also we are going to study the characteristics
and capacity for multilane highways. Free-?ow speed is an important parameter that is being
used extensively for capacity and level-of- service analysis of various types of highway facilities.
23.2 Multilane Highways
A highway is a public road especially a major road connecting two or more destinations. A
highway with at least two lanes forthe exclusive use of tra?c in each direction, with no control
or partial control of access, but that may have periodic interruptions to ?ow at signalized
intersections not closer than 3.0 km is called as multilane highway. They are typically located
in suburban areas leading to central cities or along high-volume rural corridors that connect
two cities or important activity centers that generate a considerable number of daily trips.
23.2.1 Highway Classi?cation
There are various ways of classi?cation of highways; we will see classi?cation of highways
according to number of lanes.
• Two lane highways.
• Multilane highways
Dr. Tom V. Mathew, IIT Bombay 23.1 February 19, 2014
Transportation Systems Engineering 23. Multilane Highways
                                                    Figure 23:1: Divided multilane highway in a rural/suburban environment
Figure 23:2: Undivided multilane highway in a rural/suburban environment
23.2.2 Highway Characteristics
Multilane highways generally have posted speed limits between 60 km/h and 90 km/h. They
usuallyhavefourorsixlanes,oftenwithphysicalmediansortwo-wayrightturnlanes(TWRTL),
although they may also be undivided. The tra?c volumes generally varies from 15,000- 40,000
vehicles per day. It may also go up to 100,000 vehicles per day with grade separations and no
cross-median access. Tra?c signals at major intersections are possible for multilane highways
which facilitate partial control of access. Typical illustrations of multilane highway con?gura-
tions are provided in Fig. 23:1 and 23:2
23.3 Highway Capacity
Animportantoperationcharacteristicofanytransportfacilityincludingthemultilanehighways
is the concept of capacity. Capacity may be de?ned as the maximum sustainable ?ow rate at
which vehicles or persons reasonably can be expected to traverse a point or uniform segment of
Dr. Tom V. Mathew, IIT Bombay 23.2 February 19, 2014
Transportation Systems Engineering 23. Multilane Highways
Table 23:1: Free ?ow speed and capacity for Multilane highway
Types of facility Free ?ow Capacity
speed(kmph) (pcphpl)
Multilane 100 2200
90 2100
80 2000
70 1900
a lane or roadway during a speci?ed time period under given roadway, tra?c, environmental,
and control conditions; usually expressed as vehicles per hour, passenger cars per hour, or
persons per hour. There are two types of capacity, possible capacity and practical capacity.
Possible capacity is de?ned as the maximum number of vehicles that can pass a point in one
hour under prevailing roadway and tra?c condition. Practical capacity on the other hand is
the maximum number that can pass the point without unreasonable delay restriction to the
average driver’s freedom to pass other vehicles. Procedure for computing practical capacity for
the uninterrupted ?ow condition is as follows:
1. Select an operating speed which is acceptable for the class of highways the terrain and
the driver.
2. Determine the appropriate capacity for ideal conditions from table 1.
3. Determine the reduction factor for conditions which reduce capacity (such as width of
road, alignment, sight distance, heavy vehicle adjustment factor).
4. Multiply these factors by ideal capacity value obtained from step 2.
23.4 Level of Service
Level of service (LOS) is a qualitative term describing the operational performance of any
transportation facility. The qualitative performance measure can be de?ned using various
quantitative terms like:
1. Volume to capacity ratio,
2. Mean passenger car speed,( in km/h)
Dr. Tom V. Mathew, IIT Bombay 23.3 February 19, 2014
Transportation Systems Engineering 23. Multilane Highways
Figure 23:3: LOS A
3. Density, (in p/kmln).
Basically any two of the following three performance characteristics can describe the LOS for a
multilane highway. Each of these measures can indicate how well the highway accommodates
thetra?cdemandsincespeeddoesnotvaryoverawiderangeof?ows, itisnotagoodindicator
ofservice quality. Densitywhich isameasureofproximity ofothervehicles inthetra?cstream
and is directly perceived by drivers and does not vary with all ?ow levels and therefore density
is the most important performance measure for estimating LOS. Based on the quantitative
parameter, the LOS of a facility can be divided into six qualitative categories, designated as
LOS A,B,C,D,E,F The de?nition of each level of service, is given below:
23.4.1 Level of Service A
Travel conditions are completely free ?ow. The only constraint on the operation of vehicles
lies in the geometric features of the roadway and individual driver preferences. Lane changing,
merging and diverging manoeuvre within the tra?c stream is good, and minor disruptions to
tra?c are easily absorbed without an e?ect on travel speed. Average spacing between vehicles
is a minimum of 150 m or 24 car lengths. Fig. 23:3 shows LOS A.
23.4.2 Level of Service B
Travel conditions are at free ?ow. The presence of other vehicles is noticed but it is not a con-
straint on the operation of vehicles as are the geometric features of the roadway and individual
driver preferences. Minor disruptions are easily absorbed, although localized reduction in LOS
arenoted. Average spacing between vehicles isaminimum of150mor24carlengths. Fig.23:4
below shows LOS B.
Dr. Tom V. Mathew, IIT Bombay 23.4 February 19, 2014
Transportation Systems Engineering 23. Multilane Highways
Figure 23:4: LOS B
Figure 23:5: LOS C
23.4.3 Level of Service C
Tra?c density begins to in?uence operations. The ability to manoeuvre within the tra?c
stream is a?ected by other vehicles. Travel speeds show some reduction when free-?ow speeds
exceed 80 km/h. Minor disruptions may be expected to cause serious local deterioration in
service, and queues may begin to form. Average spacing between vehicles is a minimum of 150
m or 24 car length. Fig. 23:5 shows LOS C.
23.4.4 Level of Service D
The ability to manoeuvre is severely restricted due to congestion. Travel speeds are reduced
as volumes increase. Minor disruptions maybe expected to cause serious local deterioration in
service, and queues may begin to form. Average spacing between vehicles is a minimum of 150
m or 24 car length. Fig. 23:6 shows LOS D.
Figure 23:6: LOS D
Dr. Tom V. Mathew, IIT Bombay 23.5 February 19, 2014
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