CE 578 Highway Traffic Operations Lecture 7: Two-lane highway performance

Objectives Application of operations performance measures Relate measures to field observation Roughly identify means to obtain measures

What are we trying to do with performance measures? How well does the facility serve the public? Assess performance that addresses different issues – passing demand and supply – speed impeded by geometry – speed impeded by traffic

How should we obtain two-lane highway performance? field measurement – expensive – only for existing facilities – closer to reality modeling – more cost effective – supports alternative analysis – must be validated

What are some useful performance measures? Average Travel Speed (ATS) Percentage of free flow speed (PFFS) Percent Time Spent Following (PTSF) Percent delay (PD)

Roadway and Traffic Stream Characteristics horizontal curves impeding speed horizontal curves impeding sight distance vertical curves impeding sight distance grade impeding vehicle performance entering traffic exiting traffic intersection traffic control (yield, stop, signalized) passing traffic control auxiliary lanes traffic volume opposing traffic volume heavy vehicles

How do we accommodate varying characteristics? Create highway homogenous segments Homogeneous operational effects within a segment Possess input data required to assess performance

Defining Segments and Their Borders? Grade Intersection Auxiliary lanes Horizontal curves Passing zones Volume level

Modeling Performance Stochastic micro-simulation – Washburn – TWOPAS – Paramics Deterministic model – Romana – Poulus – Troutbeck – Highway Capacity Manual (HCM)

Assignment Stochastic micro-simulation – Read paper by Yu How does this paper address the problem non-homogeneous highway characteristics? What additional segment types would you add, in addition to the ones they define? Why? Deterministic model – Read paper by Romana Why would a speed-flow model be useful? Does this one look reasonable? Explain. – Read paper by Polus What is(are) the performance measure(s) that Polus proposes? What are the steps that you would take to implement them?