1 / 26

SHRP 2 Project L07: 

Evaluation of the Costs and Effectiveness of Highway Design Features to Improve Travel Time Reliability. SHRP 2 Project L07: . Objectives for L07. Identify All Roadway Design Features Used to Improve Travel Time Reliability and Reduce Delays From Non-Recurrent Congestion

saeran
Télécharger la présentation

SHRP 2 Project L07: 

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Evaluation of the Costs and Effectiveness of Highway Design Features to Improve Travel Time Reliability SHRP 2 Project L07: 

  2. Objectives for L07 • Identify All Roadway Design Features Used to Improve Travel Time Reliability and Reduce Delays From Non-Recurrent Congestion • Assess Their Costs and Effectiveness at Improving Travel Time and Safety • Provide Usage Recommendations Via Design Guides

  3. Objectives for L07 Identify All Roadway Design Features Used to Improve Travel Time Reliability and Reduce Delays From Non-Recurrent Congestion • Traffic Incidents • Weather • Demand Fluctuations • Work Zones • Special Events • Traffic Control Devices

  4. Objectives for L07 Identify All Roadway Design Features Used to Improve Travel Time Reliability and Reduce Delays From Non-Recurrent Congestion • “The level of consistency in travel conditions over time, measured by describing the distribution of travel times that occur over a substantial period of time.”

  5. Measuring Reliability • Travel Time Index (TTI): The ratio of the actual time spent traversing a given distance to the free-flow travel time for that same distance. • Ex: 60 mph free-flow over 2 miles • Takes driver 2.5 min, normally takes 2.0 min • TTI = 2.5/2.0 = 1.25

  6. Solution: The Cumulative TTI Curve

  7. Solution: The Cumulative TTI Curve • Lateness Index Total Delay = LI × V × TTFF LI = Lateness Index V = Volume TTFF = Free Flow Travel Time

  8. Solution: The Cumulative TTI Curve

  9. Sources of Data • Crash data from HSIS • Total crashes, Fatal/Injury, Property Damage Only • Weather Data from NCDC • 10 yrs of hourly precip data across US • Focus Groups with Highway Agencies • What design treatments are you using?

  10. Objectives for L07 • Identify All Roadway Design Features Used to Improve Travel Time Reliability and Reduce Delays From Non-Recurrent Congestion

  11. Crash data from HSIS • Total crashes, Fatal/Injury, Property Damage Only • Weather Data from NCDC • 10-years of hourly precip data across US

  12. Design Treatments • Emphasis on Design Treatments that Targeted Nonrecurring Congestion • Adding a shoulder for crash investigation/ vehicle pullout vs. widening lanes

  13. Objectives for L07 • Identify All Roadway Design Features Used to Improve Travel Time Reliability and Reduce Delays From Non-Recurrent Congestion • Assess Their Costs and Effectiveness at Improving Travel Time and Safety • Provide Usage Recommendations Via Design Guides

  14. Factors in Forecasting Reliability • (1) A general measure of highway congestion (ratio of demand to capacity) • (2) A measure of temporal-spatial impacts of incidents and work zones (lane-hours lost) • (3) A measure of precipitation amount over a specified period (rain and snow)

  15. About The Research • Three separate analyses conducted • Analyze improvement in TTI • Analyze improvement in safety • Analyze costs/benefits based on these improvements

  16. Analyzing Treatment Effects • Direct calculation of performance measures from field data • Deterministic analysis techniques [using HCM] • Microscopic traffic simulation • Qualitative methods, where necessary

  17. Deriving TTI Curves • Drew on formula developed in L03 • TTIn% = e(j*LHL + k*dc + l*R) • TTIn% = nth-percentile TTI value • LHL = lane-hours lost • dccrit= critical demand-capacity ratio • R0.05” = hours of rainfall exceeding 0.05 in • jn, kn, ln= coefficients for nth percentile

  18. Estimating Demand and Capacity • Volume, speed data gathered in 5-min intervals where mean speed drops into congested range • Traffic queue forms, begins to dissipate midway through congested period • Total demand estimated (Method discussed in L03) • Alternative: d= v30 + q

  19. Estimating Demand and Capacity • Capacity (c) = Free flow speed * lanes • Capacity can be varied through strategies such as reversible lanes • Dccrit = d/c

  20. Estimating ILHL • ILHL: The effective number of lanes blocked due to all incidents occurring during a timeslice, multiplied by the average blockage time for each incident type.

  21. Estimating ILHL • Number of incidents of each type calculated using data collected for frequency of incident types as a function of traffic density • # Lanes Blocked = Total Lanes*(1-Rcap,i) • R = capacity reduction ratio for incident type i • Values of Ri found in HCM • Incident Time:

  22. Deriving TTI Curves • Drew on formula developed in L03 • TTIn% = e(j*LHL + k*dc + l*R) • TTIn% = nth-percentile TTI value • LHL = lane-hours lost • dccrit= critical demand-capacity ratio • R0.05” = hours of rainfall exceeding 0.05 in • jn, kn, ln= coefficients for nth percentile

  23. Objectives for L07 • Identify All Roadway Design Features Used to Improve Travel Time Reliability and Reduce Delays From Non-Recurrent Congestion • Assess Their Costs and Effectiveness at Improving Travel Time and Safety • Provide Usage Recommendations Via Design Guides

  24. What Does the Tool Do? • Analyzes homogenous freeway segment between interchanges • Calculates base reliability from inputs • User inputs basic data about treatment • Generally just% incidents that will use it, approx duration of incidents with treatments • Estimates new TTI curve and runs cost/benefit analysis

  25. Demo Tool!

  26. Questions?

More Related