A new shopping center is going to be constructed nearby and will bring an additi

Question

A new shopping center is going to be constructed nearby and will bring an additional 2,625 vehicles (total of both directions) to this roadway in the peak hour.  For this new mall, 3 access points will be added along the segment.  Assume all other factors stay the same.  

The following variables are for the existing roadway before the shopping center and shopping center traffic is added (i.e. the pre-existing condition):

-2 lane highway

-1 mile in length

-rolling terrain

-11-ft lanes

-5-ft shoulder

-5 access points

-60% no-passing zones

-565 two-way peak hour volume (veh/h)

-Directional split= 60/40

-PHF= 0.95

-8% trucks

-BFFS= 55 mi/h

Please modify the above variables based on the multilane highway analysis problem provided in class. In other words, this two-lane highway is to be modified by widening the highway when the shopping center is built.

Solve for the following:

How many lanes need to be added to this roadway segment to accommodate this new flow rate with a level of service no worse than B?

What is the v/c for this new condition?

How many vehicles can be added to the peak hour flow rate before reaching LOS E? (assume a minimum of two lanes in each direction or how many lanes need to be added per step 1 of the problem- whichever is greater- you are calculating how much future growth can be accommodated)

Explanation / Answer

Given:

solution:

1. How many lanes need to be added to this roadway segment to accommodate this new flow rate with a level of service no worse than B?

FFS = BFFS - fLW - fLC- fN - fID

FFS= free-flow speed (mi/h);

BFFS= base free-flow speed, mi/h = 55mi/h

( from Guidelines provided in the HCM)

fLW= adjustment for lane width from(mi/h) = 1.9mi/h

fLC= adjustment for right-shoulder lateral clearance from(mi/h) = 0.6 mi/h

fN= adjustment for number of lanes from(mi/h) = 4.5mi/h

fID= adjustment for interchange density from(mi/h) = 2.5mi/h

FFS = 55-1.9-0.6-4.5-2.5 = 45.5mi/h

Vp =              V               

              PHFxNx fHVxfP

Vp = 15min passenger car equivalent flow rate (pcphpl)

V = hourly volume = 545 (veh/h)

PHF = peak hour volume = 0.95

N = number of lanes

fHV = heavy vehicle adjustment factor

fHV =    1   

          1+ PT(ET -1 + PR( ER -1)

fHV= heavy-vehicle adjustment factor,

PT= proportion trucks and buses in the traffic stream =8%

PR= proportion recreational vehicles in the traffic stream =2%

ET= passenger car equivalency for trucks and buses,from Tables 6.7= 2.5 for rolling

ER= passenger car equivalency for recreational vehicles,from Tables 6.7 = 2.0 for rolling

fP = driver population factor = 1.0

fHV =    1 = 0.877

          1+ 0.08(2.5-1) + 0.02( 2.0-1)

LOS                    A                       C

LANE    1    3

FFS                   45.5                   47.2

fHV                            0.877               0.877

fP                              1.0                     1.0

VP                           339.07     226.04   

   2) What is the v/c for this new condition?             

Volume capacity ratio (V/C) = 565

                                            2625

                          v/c= 0.27

3) How many vehicles can be added to the peak hour flow rate before reaching LOS E?

   DDHV = KxDxAADT

AADT = DHV

             KxD

DHV = design hourly volume

D=density

AADT =2625           

            (0.98x0.6)

No. of vehicles that can be added = 4464.28 vehicles

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