Guide for Highway Capacity and Operations Analysis of Active Transportation and Demand Management Strategies
8 Summary
The Methodology for Capacity and Operations Analysis of ATDM (ATDM Analysis method) requires the following inputs in addition to the data that would normally be required for a conventional operations analysis of the facility:
- data on the variability of demand;
- collision records or incident logs; and
- weather data.
The incident log documents the frequency of lane closures due to incidents. The weather data documents the typical frequency of bad weather events for the facility.
Archived demand data for the facility is desirable to produce an accurate profile of demand variability over the course of a year. However, demand profiles can be borrowed from a nearby permanent count station for a similar facility, when archived data is not available.
Archived travel time data for the facility is desirable to better calibrate the predicted variability of facility performance over the course of the year.
The ATDM Analysis method produces the following outputs in addition to the full spectrum of outputs produced by a conventional HCM analysis:
- Average annual performance inclusive of incidents, weather, and work zones; and
- Expected 80th and 95th percentile worst performance (measures of travel time reliability).
The ATDM Analysis methodology is implemented within the context of a traditional macroscopic Highway Capacity Manual (HCM) analysis. However, the general framework employed in the ATDM Analysis allows the analyst to substitute for the conventional HCM tool any facility operations analysis tool deemed appropriate, including mesoscopic and microscopic simulation tools.
While an analyst with sufficient resources available can use a traditional regional demand model to assess the effects of ATDM strategies on demand, the recommended ATDM Analysis methodology provides a sketch planning approach for estimating these effects when the questions being studied do not warrant such an extensive analytical investment.
The Methodology for Capacity and Operations Analysis of ATDM includes a demand and capacity scenario generation method which enables analysts to estimate the current distribution of travel times for their facility when archived travel time data is not available. This method was found to be superior at predicting the yearlong variation in facility performance compared to taking a nine-day sample of facility travel times.
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