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Washington Division |
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Washington Divison |
EVALUATION PLAN TO EXAMINE THE EFFECTS OF
CHANGES IN HOV LANE HOURS OF OPERATIONINTRODUCTION
The Washington State Department of Transportation (WSDOT) currently uses an operating policy that reserves HOV lanes on the Puget Sound Region's freeway system as HOV only 24 hours per day, 365 days per year. The WSDOT, and the Washington Transportation Commission has proposed to modify the operating policy to allow general purpose vehicle use of the HOV facilities between 7 pm and 5 am on portions of I-405, I-90, SR 167, and SR 520. HOV direct access ramps will remain restricted to HOV only, 24 hours a day.
Prior to the change in operating policy, the Department will implement a number of safety improvements to mitigate the potential reduction in safety caused by having additional vehicles traveling in the left-most lane of a freeway which results in a reduced recovery distance for those vehicles and a possible increase in crashes if left unmitigated.
The Department and Commission need to understand the effects of these changes, in order to judge whether the policy changes should be permanently adopted. This document describes the analyses that will be performed to evaluate the effects of the combination of safety improvements and revised HOV operating rules.
PROJECT OBJECTIVES
The change in HOV policy is designed to allow increased use of the HOV facility at times during which it is not needed for maintaining the reliability of transit service. At the same time, the project is intended to maintain and/or increase public support for the HOV program, while maintaining or increasing safety within the effected corridors. Lastly, the new policy is intended to provide some additional congestion relief for general purpose vehicles, without causing degradation of HOV lane performance. HOV performance includes HOV lane violation rates, and facility congestion during the remaining time periods where HOV lane use is restricted to HOVs. General purpose lane congestion will be analyzed during these same time periods.
TASK PLAN
To measure the effects of the new HOV lane policy, the WSDOT will track the following basic measures of effectiveness.
The project will also examine traffic operations in the Bellevue area prior to and after opening the Bellevue direct access ramp and at freeway to freeway connections affected by the now permissible uses of the HOV lanes. In addition to the above measurements these movements will be examined for the occurrence of unsafe driving behavior (weaving, sudden lane changes). Specific measures of effectiveness for analyzing these facility changes will be worked out with WSDOT staff at the start of this analysis.
The data to be collected, and the analysis to be performed for each of these subject areas are discussed in the seven tasks presented below. These tasks are:
The work to be performed in each of these tasks is discussed in the following subsections. All evaluation efforts will be coordinated with the WSDOT Public Information Office.
Vehicle Occupancy Study
The WSDOT will fund an expansion of their current vehicle occupancy data collection program. The expansion will entail collection of vehicle occupancy data during the first two hours of HOV lane operation in the morning, and the last two hours of HOV lane operation in the evening. Data will be collected prior to the implementation of the new policy and annually thereafter until June 2005. It is anticipated that the "prior" data collection will take place in May 2003, with the initial "after" data collection effort taking place (light permitting) in late Summer or early Fall of 2003
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Data will be collected at 10 locations on (four on I-405, two on SR 167, one on I-90, one on SR 520, and two control sections on I-5.) The existing HOV lane vehicle occupancy monitoring program will remain in force during these time periods. Ramp violations at the Bellevue direct access ramp will be collected following opening. This is expected to be in Fall of 2005. Ramp violations before and after at three ramp meter locations will be collected.
The occupancy count data will be used to determine
The vehicle occupancy data, along with transit ridership data collected as part of this task from the various transit authorities, will also be used to determine person throughput on the HOV lanes.
Traffic Evaluation
The traffic evaluation will use the existing WSDOT FLOW traffic data archive to measure facility vehicle usage and facility performance before and after the HOV policy change. Existing FLOW analysis tools will be used to determine if significant increases in HOV lane volumes occur once the HOV lane restriction is removed. The volume changes by time of day will be compared at a variety of locations within the study area, and will also be compared across locations. Of additional interest will be a comparison of the predicted shift in lane distribution versus the measured shift in lane distribution.
The FLOW data will also be used to measure the facility travel times (by time of day), and the frequency and location of congestion within the various study corridors. Data on all of these subjects are collected automatically and continuously. This allows analysis of various time periods to be examined. So, for example, in addition to basic before / after time periods, this evaluation will look at the effect on roadway performance of the opening of the Downtown Bellevue direct access ramp. In addition, analyses will be performed that examine changes in facility performance immediately after the policy changes, and after the public has had a chance to get used to the new operating policy (e.g., one to two months later.) An assessment of the overall congestion benefits will be performed in terms of person, transit and vehicle delay.
Safety Evaluation
The evaluation will use accident and incident data available near the end of the demonstration (we assume data will be available for 2003 and 2004) to study the safety effects of the HOV policy change. The safety analyses will concentrate on changes in run-off-the-road accidents, as well as the accident histories of known weaving locations, freeway to freeway HOV ramps and high accident sites within the study corridor. These accident and incident histories will be compared against the available traffic volume data to determine if changes in accident and incident rates take place, as well as the overall number of accidents and incidents.
Observed values will be compared to those predicted by WSDOT when the policy change was being considered.
Enforcement Evaluation
In this task, WSDOT will summarize the enforcement actions taken before and after the policy goes into effect. If WSP can make the data available, this will include the number of hours of enforcement provided, the location of those enforcement efforts, and the number of citations issued as a result of those enforcement actions.
In addition, the number, location and time of HERO Hotline reports of HOV violations will be analyzed and reported.
These two basic data sources (WSP citations and HERO reports) will be used to develop estimates of changes in the frequency of HOV lane violations. These estimates will be compared with estimates of the change in HOV violation rates obtained from the vehicle occupancy counting program discussed in Task 1. As part of this analysis, specific attention will be made to changes that occur immediately after the opening of the Direct Access Ramps in Bellevue.
Air Quality Evaluation
At the end of the first year of the pilot WSDOT will use the traffic data collected from this monitoring effort to select key locations where there is good baseline data to evaluate operation of the system in relation to air quality performance. If traffic data indicates reductions in speed and system performance as a result of the conversion to general purpose use (for example, outside of the normal fluctuations of economic cycles, regional growth, and unforeseen traffic incidents), WSDOT will conduct air quality analysis to model changes in air emissions. This evaluation will cover select periods in evening/morning shoulder times and midnight. The results of this review (of traffic only or full air quality if traffic conditions change as a result of the HOV conversion) will be provided to appropriate air quality stakeholders (EPA, Ecology, and Puget Sound Clean Air).
At the end of the first and second years WSDOT will report a trend line for select locations of the converted system to show speed changes on the system over time.
At the end of the two-year pilot, the WSDOT will again review traffic data for changes in speed and congestion parameters to determine the effects of the HOV conversion. The WSDOT will provide a qualitative discussion of air quality in relation to traffic parameters if there are no substantive changes that affect air quality. The WSDOT will perform further quantitative air quality analysis/modeling using traffic data if changes in traffic is warranted per discussion in the paragraph above.
Opinion Surveys
WSDOT will survey several different groups as part of this study. These groups include the general public, individuals that travel in the corridors affected by the policy change, key public officials, and key interest groups.
Mail surveys will be used for gathering public opinion for the general population and for persons who travel within the corridor. Individual interviews will be performed with public officials and key interest groups in order to obtain their reactions towards the new HOV policy. Opinion data will be obtained prior to the start of the new policy, and then again roughly two-thirds of the way through the pilot project.
These data will then be analyzed to determine whether the public's attitude towards HOV lanes has changed as a result of the new operations policy.
Under this task, evaluation staff will work with the local transit agencies to determine if transit operations are effected in any way by the policy shift. (Note that the policy shift is designed to allow general purpose traffic into the HOV lanes only when transit vehicles do not need those lanes, so transit impacts are expected to be minimal, and little field data collection is assumed necessary to collect transit ridership or transit performance data.)
Report Generation
For this evaluation, WSDOT will produce three formal reports and a variety of interim working papers and presentations. A report will be issued at the end of each of the two years the pilot demonstration is in place, as well as shortly after the revised policy is first implemented. The final report for the project (the third report) will be submitted to FHWA and their designees in draft form, and then revised in response to comments received from FHWA.
Project presentations will be made on request to the State Transportation Commission. These presentations are expected to occur approximately every six months. Additional presentations to interested public officials, agencies, or interest groups will be made as requested. In addition, the evaluation team will work with WSDOT's Public Information Officers to take the information incorporated in to these presentations and the three formal reports to provide community outreach through WSDOT's web site and those other mechanisms selected by WSDOT.
SCHEDULE
The pilot demonstration will last two years. Data collection for this project will start prior to the demonstration itself, in order to obtain an accurate measurement of "before" conditions. Data collection is expected to start in May 2003. The duration of this evaluation effort is expected to be roughly 30 months.
STAFFING
It is currently expected that this project will be performed by a combination of WSDOT staff and staff from the Washington State Transportation Center (TRAC). The budget for the two-year evaluation is expected to be approximately $200,000.
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