Lec 17, Supply Analysis Part 1: Role of supply analysis (ch7.1) and Analysis of system performance (ch7.2)
The role of performance analysis in transportation planning
Performance measures used Performance analysis concepts(The topics described in 7.2 are the major
topics of CEEn 562 Traffic Engineering & CEEn Traffic Simulation and Signal Optimization. Hence we touch only the basics, or general concepts, in this class.)
Transportation system components & supply analysis
System user
Mode or technology of travel
Stake holdersIntermodal connections
for transfers
Infrastructure that allows travel to occur
Supply Analysis:Evaluate the characteristics
of infrastructure
From ROW to service frequency – anything that is needed to provide transportation to the user
(5 major components of the transportation system)
The role of supply analysis in TP
Developing and managing the supply of transportation is a primary focus of an effective transportation planning process.
Analysis results are used at different levels of decision making
Metropolitan-level network analysis for strategic investment
Operational or tactical planning
Scheduling of transportation services
Supply analysis in transportation planning
Two perspectives
The user User optimal
The (system) operator System optimalUser optimal solutions are
not always system optimal, e.g., Everyone wants to drive because it is convenient (user optimal), but congestion occurs and air is polluted more than necessary (System is not at optimum).
In order to estimate system impacts and costs, one must first estimate system performance.
(See p.387-390 for the explanations of the 4 “linkages” shown.)
Characterization of a transportation system: We can analyze the characteristics of the supply from different perspectives.
Performance
Impacts Costs
e.g. Travel times, frequency of service, safety, and reliability
e.g. Environmental and social/cultural
e.g. Capital cost, operation cost, maintenance/rehab cost
Focus of this lecture
Network representation of the real system
QRS II representation of the network
Network characteristics, typical ones for highways/streets:
Speed: Avg. running speed, avg. travel speed, space mean speed, time mean speed, free flow speed
Volume or flow rate
Density, vpm or vpk
Capacity
Level of service
Fuel use
Air pollutionFor uninterrupted flow, major characteristics are related. (Do you remember what you did in CE361?)
7.2.2 Performance analysis concepts
Time-space diagrams (micro)
Queuing theory (macro)
Fluid-flow approximation (macro)
Simulation (micro)
Mathematical programming (macro)
These are covered in CE561, CE562, and CE662.
Simulation example: CORSIM
Simulating an incident. CORSIM can simulate multiple time periods.