Travel Time Estimation on Arterial Streets

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• Travel Time Estimation on Arterial Streets
• By
• Heng Wang, Transportation Analyst
  Houston-Galveston Area Council
• Dr. Antoine G Hobeika, Professor Virginia Tech

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Outline

• Objective and background
• Focusing methodology development
• Methodology validation
• Conclusion and future study
• Q A

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Objective

• Methodologies were prepared for the proposal for
  real-time travel time estimation on major
  arterial streets.
• Requirements
• Short time interval update for real-time
  estimation
• Simple-computation time
• Make good use of real time detected traffic
  information
• Well behaved

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About the Methodology

• The developed methodology is presented into two
  sections
• 1. Travel time estimation on an isolated
  arterial link
• 2. Travel time estimation on a signalized
  arterial link that also considers the traffic
  situation on the upstream and downstream
  links(Network Algorithms).

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Section 1- Travel time estimation on an isolated
arterial link --Travel Time Components

• Travel time(HCM)link travel time intersection
  control delay
• Components of intersection control delay
• 1) Uniform delay
• 2) Incremental delay (over-saturation delay)
• 3) Initial delay

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Intersection Control Delay (HCM2000) and its
weakness in short time period update situation

• Uniform Delay
• Incremental Delay
• Initial Delay

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Developed Algorithms--Intersection Control Delay
-Observed Vehicle Group Identification
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Developed Intersection Control Delay Algorithms

• Case 1-where there is no initial queue for the
  observed vehicle group
• Case 2-there is an initial queue for the observed
  vehicle group and its clearance time is less than
  a cycle length
• Case 3- where initial queue clearance time (d3)
  is greater than a cycle length.

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Intersection Control Delay- Case 1 no initial
queue
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Intersection Control Delay-Case 2 an initial
queue exists and it is smaller than one cycle
length( 0ltd3ltCL)
g1d3-r
situation
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Intersection Control Delay-Case 3 -Initial Queue
clearance time d3 is greater than one cycle
length (d3gtCL)
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Validation of Intersection Control Delay
Algorithms

• An intersection at N Franklin St/Peppers
  Ferry RD in Christiansburg, Virginia was selected
  to initially conduct control delay analyses based
  on traffic volume and the arrival of vehicles in
  the observed group.

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Validation of Intersection Control Delay
Algorithms
MAE for developed algorithm result with real
control delay 10.85sec MAE for HCM2000 algorithm
result with real control delay14.28sec
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Validation of Intersection Control Delay
Algorithms
ANOVA Table for Actual Delay vs HCM2000 results
Source DF SS MS F P
Regression 1 472.2 472.2 1.82 0.182
Residual Error 26 6733.4 259.0
Total 27 7205.7
ANOVA Table for Actual Delay vs Developed
Algorithm results
Source DF SS MS F P
Regression 1 4267.4 4267.4 37.76 0.01
Residual Error 26 2938.3 113
Total 27 7205.7
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Total Travel Time Computation

• Travel Time Without initial Queue
• Travel time with an initial queue but without
  blackout
• Travel time with blackout (i.e. QLgt LTD)

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Section 2- Network Algorithms

• Network conditions that influence input
  parameters
• Bottleneck on the downstream link
• Change intersection capacity
• Blackout Situation
• Change the identification of the
  observed vehicle group.

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Algorithm 1(No blackout)
Is departing rate from link i smaller than
downstream links capacity?
Yes
No
Use intersection capacity of link i
Use downstream lane capacity as the intersection
capacity of link i
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Algorithm 2(Determining the intersection capacity
of link i when blackout is on the downstream link
i1)
Is Li1 -QLi1lt100ft? (High congestion
downstream?)
Yes
No
Use the detected flow rate from downstream
detector as the intersection capacity of link i
Algorithm 1
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Algorithm 3(Determining incoming volume when
blackout is on link i)
Is Li Qligt100ft High congestion on link i?)
Yes
No
Use the dissipated volume from link i-1 as the
incoming volume to link i
Use the smaller of the following two values a)
the dissipating rate from link i-1 b) the
intersection capacity of link i which is the
maximum dissipating rate of link i
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Algorithm 4 (Where no detectors are available
beyond this link)
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A Simulation from CORSIM
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Results
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Conclusion and future study

• Algorithms in section 1 provide accurate results
  when compared with HCM2000 by using real world
  data
• Algorithms in section 2 are robust when compared
  with CORSIM simulation results
• Real world data would be collected to validate
  the section 2 of the developed methodology.

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Questions?