TRAFFIC OPERATIONS REVIEW

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TRAFFIC OPERATIONS REVIEW
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Speed Studies

• Time mean speed vs. space mean speed
• Definition
• How to estimate?
• Grouped sample set
• Normal distribution
• Use its properties
• Sample size issue
• Compare two sets of samples

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Traffic Studies

• Volume studies
• Terms
• How to measure?
• Travel time
• Terms
• How to measure?
• Safety
• Terms

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Traffic Measurements

• Traffic parameters
• Flow (q) vph
• Volume (v) vph
• Density (k) vpm
• Speed (u) mph
• Time Headway (h) sec/veh
• Gap (g) sec/veh
• Space Headway (s) ft /veh
• Spacing (S) ft/veh

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Traffic Measurements

• Definitions
• How to measure each parameter from the time-space
  diagram
• Basic equations
• qku
• Greenshields uufuf/kj k

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Speed-Flow-Density Relationship
uf
uo
qmax
qmax
Capacityqmax
kj
ko
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Example 1
q 50k 0.90k2 uf kj ko uo qmax?
qk u Y
k u 50k -0.90k2 Y
u 50 -0.90k
Greenshields
uf 50 mph
kj 55.56 vpm
0.90uf /kj Y
uo uf/2 25.0 mph
qmax kj uf/4 694.5 vph
ko kj/2 27.78 vpm
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Example 2
Spacing 200 ft/veh _at_ q1188vph Greenshileds with
uf 60 mph kj qmax?
k 5280/s 26.4 vpm
u q/k 45 mph
q 1188 vph
Greenshields Y
uuf uf/kjk Y
4560-(60/kj)26.4
qmax kj uf/4 1584 vph
kj 105.6 vpm
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Capacity Analysis

• Basic Procedure
• Estimate FFS
• Estimate equivalent flow rate (vp)
• Calculate density and find LOS from diagram

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Type of Facilities

• Freeway
• Multilane highway

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Calculation Procedures

• Estimate free flow speed (FFS) of cars
• Exhibits 23-4 through 23-7 FREEWAYS
• Exhibits 21-4 through 21-7 HIGHWAYS
• Calculate service flow rate (vp)
• Compute density (Dvp/u)
• Compare D to determine LOS to values in
• in Exhibit 23-3 FREEWAYS
• in Exhibit 21-3 HIGHWAYS

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Example 1 (1/3)
4-Lane rural freeway V1,900 vph 5 trucks
11-foot lanes 3-foot right and left shoulders
2 grade 0.85 miles 0.5 interchanges/mile
PHF 0.9 everyday commuters. LOS?
FFS BFFS - fLW - fLC - fN - fID
71.3 mph
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Example 1 (2/3)
1111 pcphpl
0.95
fhv 1/1PT(ET-1)PR(ER-1)
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Example 1 (3/3)
D vP/FFS 1111/71.3 15.58 pcpmpl