Forecasting Transit Speed and Delay for Planning Applications in Florida

Document Type

Journal Article

Publication Date

2007

Subject Area

land use - planning, ridership - forecasting, ridership - forecasting, mode - bus

Keywords

Travel time, Transportation planning, Speed, Scenarios, Projections, Peak periods, Off peak periods, Journey time, Jacksonville (Florida), Intracity bus transportation, Forecasting, Bus transit

Abstract

The Florida Department of Transportation sponsors automobile speed and delay studies for the purpose of calibrating regional transportation planning models, so that modeled link speeds more closely reflect existing conditions. In contrast, the models’ bus speeds are typically not calibrated. As a result, it is difficult to assess accurately the impact of future traffic conditions and project alternatives on future bus speeds; this in turn makes it difficult to plan for a more multimodal transportation system in the long term. To address this issue, the department sponsored simultaneous speed and delay studies in 2005 in the Jacksonville region for the automobile and bus modes. Four sets of models were developed from the collected data, which estimate bus speeds as functions of both auto speeds and planning-level attributes (e.g., daily traffic volumes, roadway functional class, and area type), for roadway segments and entire bus trips. The study found a linear relationship between bus and auto travel times (and speeds) across the range of sampled travel times, unlike the current regional model structure, which uses three different linear functions for various ranges of auto speeds. Bus travel times were a consistent proportion of auto travel times during peak and off-peak periods, although absolute travel times were longer during peak periods. Finally, the current model structure was found to underestimate the maximum observed bus speeds in the field. These results are consistent with those of a study conducted in the Tampa Bay area in 2003.

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