Meeting_Body
AD HOC CUSTOMER EXPERIENCE COMMITTEE
MAY 17, 2018
Subject
SUBJECT: SEVERELY CONGESTED BUS CORRIDORS
Action
ACTION: RECEIVE AND FILE
Heading
RECOMMENDATION
Title
RECEIVE AND FILE status report identifying the most severely congested bus corridors within Metro's service area.
Issue
ISSUE
As part of the NextGen Bus Study, staff has developed a tool that allows us to identify the impacts of traffic congestion on bus speeds. This report describes the methodology used in the tool, and identifies the 20 most severely impacted corridors.
Discussion
DISCUSSION
In recent years, there have been a number of studies identifying the most congested highway networks in the United States. Various cities are ranked on the basis of hours of delay experienced by commuters annually. The goal of these studies is to identify opportunities to improve traffic flow.
There are two key metrics used in these evaluations - 1) Threshold Speed defined as the uncongested speed achieved by vehicles on each highway segment, and 2) a Travel Time Index (TTI) which compares the actual travel time at any given time period to its Threshold Speed. For example, if it takes 4 minutes to travel one mile at the uncongested Threshold Speed, but 6 minutes during the congested peak period, then the Travel Time Index is 6 minutes divided by 4 minutes, or 1.5.
These metrics were originally developed at the Transportation Institute of Texas A&M University. The lowest possible value for the TTI is 1.0 which signifies travel at the uncongested speed. The Institute determined that values in excess of 1.25 constitutes severe congestion, and values in excess of 1.5 represents very severe or extreme congestion.
Staff determined that a similar metric is needed to analyze bus speeds along congested corridors in Los Angeles. The goal of this effort is to be able to determine when and where buses experience the most adverse impacts to speeds due to traffic, poor signal coordination, or ...
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