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Method and Apparatus to Create Levels of Road Network for Faster Routing in Traffic Simulation

IP.com Disclosure Number: IPCOM000224873D
Publication Date: 2013-Jan-09
Document File: 7 page(s) / 137K

Publishing Venue

The IP.com Prior Art Database

Abstract

Worked as a decision evaluator, Traffic simulation is a necessary tool in traffic operation and optimization. Modern traffic simulation systems work in a dis-aggregated manner, i.e. model behaviors person by person, vehicle by vehicle in a traffic system. In which, path-finding takes up lots of computation cost. Existing fast path finding approach takes the road network as a cost-invariant network. While in simulation, vehicle speed on road segment depends on the crowdness on the segment, which makes the network to be time-variant. This disclosure proposed a road network abstraction method leveraging both the idea of hierarchical path-finding and path assignment in traffic simulator, performing pre-computing for each OD Matrix(the key input in simulation). This approach keeps both efficiency and accuracy. 1. Leverage the input, OD matrix in simulation. OD Matrix represents the departing needs in traffic system. 2. Leverage path assignment mechanism in simulation to predict reasonable time-dependant cost on road network.

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Method and Apparatus to Create Levels of Road Network for Faster Routing in Traffic Simulation

Background:


Smart Transportation holds a significant position in Smart City strategy, which brings about many opportunities:

Transit network performance assessment

Time table optimization

Public bicycle renting point selection

Precision advertising on public transit


Traffic simulation is a necessary component in evaluation / optimization problems: Dynamic indices are inferred by traffic simulation

Timeliness is important to support decision evaluation


In traffic simulation, we simulate vehicle behavior based on the execution of trajectories

We got Input :
Road network


OD Table[*], representing the "departure need" of vehicle path [*]A table whose entry is in the form [Departure Time, Origin, Destination, Count] Paths are not attached with OD Table

Thus, a path-finding method is needed for traffic simulation

A routing method for traffic simulation requires
High efficiency

Vehicles depart in each time step, each departing vehicles needs a path assigned.

A driver may decide to change route when he/she got jammed. The starting point can be any point in network, not limited by OD Table
Running vehicles on roads "forms" the road condition, which can be regarded as a correcting to the network cost. i.e. Simple pre-computing is not available in this case

Time Variant

   Ideal path depends on road condition, which is variant compared with road network. Coarse Optimality

Even real vehicles don't care about which branch road will give seconds' benefit

Problem:

1


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2


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Main Idea:

3


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Detail Illustration - Path Assignment:

A feed-back mechanism in traffic simulation, use travel time record in previous simulation to compensate cost of road segments.

     Road Segments with lower speed wil...