Solution Manual for Traffic Engineering (5th Edition by Roess, Prassas & McShane) – Complete Problem Solutions

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SOLUTIONS

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Traffic Engineering, 5 Edition r r




Roess, R.P., Prassas, E.S., and McShane, W.R.
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SolutionstoHomeworkNo.2 r r r r




Problem 5‐1 r




A volume of 1,200 veh/h is observed at an intersection approach. Find the peak flow rate within
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the hour for the following peak-hour factors: 1.00, 0.90., 0.80, 0.70. Plot and comment on the
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results.
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Thepeakflow rateofflowiscomputed asv=V/PHF.Thetablebelowsummarizesthe results for
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the information given. A plot follows.
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Evenwiththesamehourlyvolume, a
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small difference in PHF leads to an
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enormous difference in peak flow
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rates. Traffic engineers must be able
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to deal with this peaking
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characteristic on a regular basis.
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,Problem5‐2 r




A traffic stream displays average vehicle headways of 2.4s at 55 mph. Compute the
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density and rate of flow for this traffic stream.
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Aheadwaycanbeconverted toaflowrateasfollows:
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v=3600 = 3600 =1,500 veh/hr/ln
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h 2.4

Knowingbothflowrateandspeed(given),thedensitymaynowbecomputed as:
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D = v = 1500 = 27.3 veh/hr/ln
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S 55



Problem 5‐3 r




Afreewaydetectorrecordsoccupancyof0.26fora15-minuteperiod. Ifthedetectoris
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3.5ftlong,andtheaveragevehiclehasalengthof18ft.whatisthe densityimpliedby this
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measurement?
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Densityisobtainedfromoccupancyasfollows:
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Suchahighvalueisindicativeofhighlycongestedconditionswithinaqueue.
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, Problem 5‐4 r




The following traffic count data were taken from a permanent detector location on a major
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state highway. From this data, determine (a) the AADT, (b) the ADT for each month. (c)the
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AAWT,and(d)theAWTforeachmonth. Fromthisinformation,whatcan be discerned about
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the character of the facility and the demand it serves?
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ThetablebelowillustratesthecomputationofmonthlyADTandAWTvalues.
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The AADT iscomputedasthe totalannual volumedividedby365days,or:
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AADT= 2,365,000 = 6,479 veh/day
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365

The AAWT iscomputedasthe totalweekday volumedividedby260 days,or:
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AAWT= 2,067,000 = 7,950 veh/day r r r r r




260




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