Traffic And Highway Engineering
Traffic And Highway Engineering
5th Edition
ISBN: 9781133605157
Author: Garber, Nicholas J., Hoel, Lester A.
Publisher: Cengage Learning,
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Chapter 10, Problem 5P
To determine

The capacity of the lane group.

Expert Solution & Answer
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Answer to Problem 5P

The capacity of the lane group is 723veh/h/lane.

Explanation of Solution

Given:

The base rate is 1900pc/h/lane.

Lane width is 11ft.

Heavy vehicles are 4% of the traffic stream.

Approach grade is +3%.

No on-street parking.

No bus stops.

Bicycle and pedestrian traffic conflicting with this lane group is negligible.

Intersection is in a central business district.

The effective green time for the movement is 35s.

The total cycle length is 60s.

Formula used:

The adjusted saturated flow rate for a lane group is given by

s=(s0)(fw)(fHV)(fg)(fp)(fa)(fbb)(fLu)(fRT)(fLT)(fLPb)(fRPb)   ...... (I)

Here, s is saturation flow rate for the subject lane group, s0 is a base saturation flow rate per lane, fw is the adjustment factor for lane width, fHV is the adjustment factor for heavy vehicles in the traffic stream, fg is the adjustment factor for approach grade, fp is the adjustment factor for the existence of a parking lane adjacent to the lane group and parking activity on that lane, fa is the adjustment factor for area type, fbb is adjustment factor for blocking effect of local buses stopping within the intersection area, fLu is the adjustment factor for lane utilization, is the adjustment factor for right turns in the lane group, fRT is the adjustment factor for right turns in the lane group, fLT s adjustment factor for left turns in the lane group, fLPb is pedestrian adjustment factor for left- turn movements, and fRPb is the pedestrian adjustment factor for right- turn movements.

The Heavy-vehicle adjustment factor is given by

fHV=100100+PHV(ET1)   ...... (II)

Here, fHV is Heavy-vehicle adjustment factor, PHV is percent of Heavy-vehicle in the subject improvement ground, and ET is passenger car equivalent.

The grade adjustment factor is given by

fg=1Pg200   ...... (III)

Here, fg is grade adjustment factor, and Pg is approach grade for the subject movement group.

Parking adjustment factor is given by

fp=N0.118Nm3600N0.050   ...... (IV)

Here, Nm is parking maneuver rate adjacent to lane group, and N is number of lanes in lane group.

The bus blockage adjustment factor is given by

fbb=N14.4Nb3600N0.050   ...... (V)

Here, Nb is bus stopping rate at the approach.

The lane utilization adjustment factor is given by

fLu=vgvgiN   ...... (VI)

Here, vg is unadjusted demand flow rate for lane group, and vgi is unadjusted demand flow rate on the single lane in the lane group with the highest volume.

The right turn adjustment factor for protecting movement on exclusive lane is given by

fRT=1ER   ...... (VII)

Here, ER is equivalent number of through cars for a protected right-turning vehicle the value of which is 1.18.

The left turn adjustment factor for protecting movement on exclusive lane is given by

fLT=1EL   ...... (VIII)

Here, EL is equivalent number of through cars for a protected left-turning vehicle the value of which is 1.05.

The value of fLPb, fRPb, and fLu is 1, and the value of fa is 0.90.

The capacity of the lane group is given by

c=NsgC   ...... (IX)

Here, c is capacity, g is effective green time for the lane group, C is cycle length.

Calculation:

The Heavy-vehicle adjustment factor is calculated as

Substitute 4% for PHV, and 2 for ET in equation (II).

fHV=100100+4%( 21)=100100+4 100=0.9996

The grade adjustment factor is calculated as

Substitute 3% for Pg in equation (III).

fg=13%200=13 100200=10.00015=0.999

Parking adjustment factor is calculated as

Substitute 1 for N, and 0 for Nm in equation (IV).

fp=10.1 18×0 360010.050=10.10.050=0.90.050

The bus blockage adjustment factor is calculated as

Substitute 1 for N, and 0 for Nb in equation (V).

fbb=1 14.4( 0 ) 360010.050=100.050=10.050

The right turn adjustment factor for protecting movement on exclusive lane is calculated as

Substitute 1.18 for ER in equation (VII).

fRT=11.18=0.847

The left turn adjustment factor for protecting movement on exclusive lane is calculated as

Substitute 1.05 for EL in equation (VIII).

fLT=11.05=0.952

The adjusted saturated flow rate for a lane group is calculated as

Substitute 1900pc/h/lane

0.9996 for fHV, 0.999 for fg, 0.9 for fp, and fa, 1 for fbb, 0.847 for fRT, 0.952 for fLT, 1 for fLPb, fRPb, fw, and fLu in equation (I).

s=(1900pc/h/lane)(1)(0.9996)(0.999)(0.9)(0.90)(1)(0.847)(0.952)(1)(1)(1)=1239.22veh/h/lane

The capacity of the lane group is calculated as

Substitute 35sec for g, 1239.22veh/h/lane for s, 60sec for C, and 1 for N in equation (IX).

c=(1)(1239.22veh/h/lane)( 35sec 60sec)=722.87veh/h/lane723veh/h/lane

Conclusion:

The capacity of the lane group is 723veh/h/lane.

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