Table A17 Fontaine and Edara 2007 Summary Characteristics Simulated location

Table a17 fontaine and edara 2007 summary

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Table A17. Fontaine and Edara (2007) Summary Characteristics Simulated location for 24 hour period VISSIM simulation software 8-mile mainline route, 65 mph, one alternative route Rural route used since urban drivers could have many accessible alternative routes and could be more familiar with seeking alternative routes in the area Performance Measures Diversion, Delay, and Speeds Diversion ranges from 4 to 20% but depends on volume Diversions increase when an alternative route is clearly identified rather than identifying slower speed ahead Displaying diversion routes is more useful than displaying delay times since drivers are likely to complain when delay times are incorrect Effect of congestion may have larger impact on speeds then speed advisory signs Lower speeds on alternative routes can decrease system performance if too many drivers divert Intended Benefits Benefits exceed costs when speed advisory messages or travel time or delay messages are implemented Methodology Simulation data, Washington, D.C. traffic volume data Use of peak hour volume, diversion %, alternate route speed, and daily travel time savings Findings Table results show the number of days until the benefit/cost is > 1.0 or benefit/cost could be found given a specific number of days Use of a SWZ may result in a higher benefits than cost depending on said variables In regards to why simulation is used for this study, Kushto and Schofer (2011) used simulation to measure the impacts of construction zones on drivers regarding delay. By using VISSIM, they simulated a 1.1 mile stretch of freeway with a 0.5 mile work zone using input data from the Chicago area. Diversion routes were implemented on several but not all scenarios. Measuring performance on an individual, disaggregate basis can lead to new conclusions about work zone management. One of the results found was that flow can recover faster by lowering the frequency and length of interruptions compared to just working during the off-peak period. Work zones have the lowest delays when construction interruptions are minimized compared to adding a diversion route. Because work zones have a large affect on individual drivers and delay times, this simulation approach can aid in providing guidance on when to apply ITS better manage construction practices.
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40 Garber and Ehrhart (2000) developed mathematical equations to find accident rates. The equation incorporates average speed, speed variance, geometrics of the roadway, and traffic volumes. The required data to find the accident rate included mean speed, standard deviation of speed, lane width, shoulder width, and lane flows. Mulitvariate ratio of polynomials outperformed the other deterministic models which were multiple linear regression and robust regression. A recommendation was made to apply stochastic models to accident rate equations since accidents occur randomly.
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