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I-526 Corridor Analysis Complete

The I-526 Corridor Analysis project is now complete; the final report can be found here.

An addendum to the final report is currently underway considering the impact of the proposed Charleston International Airport area projects on the I-526 study corridor, particularly at the I-526 interchanges with International Boulevard and Montague Avenue. At the conclusion of the addendum, there will be one final meeting of the Steering Committee and one last Public Information Meeting to review the final study recommendations.

December 2012 to June 2013:

The project team has prepared preliminary strategy recommendations and developed recommended concepts in each of four improvement strategy categories: Travel Demand Management Strategies (TDM); Modal Strategies; Traffic Operations Strategies; and Capacity Improvement Strategies.

These strategy recommendations have been documented in a draft report and have been developed based upon the degree of Congestion Relief, Safety, Costs, Suitability, Project Phasing, and Environmental Impacts that each provide. The preliminary recommendations indicate:

  • With consideration of full implementation of the TDM strategies, including but not limited to increased carpooling, employers providing transit passes and other incentives, work flex time, and further education/promotion/marketing, traffic volumes along the study I-526 corridor and in the Charleston County area in general could be reduced by approximately 5.2%;
  • With consideration of full implementation of the Modal strategies, including but not limited to transit route enhancements and new routes, improvement of transit facilities, and enhanced intermodal facilities, traffic volumes along the study I-526 corridor could be reduced by approximately 7.4%;
  • Numerous Traffic Operations improvements were identified and grouped by Geometric, Pavement Marking, Signing, and ITS improvements to address localized safety and congestion issues along the study corridor; and
  • The highest priority capacity improvement projects identified included improvements to the I-26 & I-526 interchange and the widening of I-526 to six lanes. These improvements could be postponed for five to 10 years with the potential traffic volume reductions of the TDM and Modal strategies.

The recommendations were presented to both the Steering Committee and Stakeholder Committee on February 27, 2013. Subsequent to the Steering and Stakeholder Committee meetings, several improvements related to Charleston International Airport and Boeing have been proposed. These improvements could have a significant impact on the study I-526 corridor; therefore, the project team will be conducting additional analyses over the next few months considering the impact of these projects on the study corridor, particularly at the I-526 interchanges with International Boulevard, Montague Avenue, and Dorchester Road. The results of the additional analyses will be presented in an addendum to the final I-526 Corridor Analysis report.

In the upcoming months, there will be two further meetings of the Steering Committee and one last Public Information Meeting, at which the Stakeholder Committee members will be invited, to review the final study recommendations.

April 2012 to November 2012:

After the preliminary analysis and concept plans were reviewed by the steering committee, the study team began to test the VISSM Traffic Analysis on the most feasible strategies and concepts. The VISSIM modeling was able to show the study team how each concept and strategy could impact the corridor's project traffic volumes.

The team held a Steering Committee and Stakeholder Committee Meetings on June 20, 2012 to discuss the results of the VISSIM traffic analyses, the development of the preferred concepts, and the refined improvement strategies. The meetings also included a spending priorities exercise for the respective groups. A summary of the progress for each of the four improvement categories is provided herein.

Travel Demand Management (TDM) Strategies: The TDM strategy evaluation efforts consisted of a review of existing case studies and evaluation utilizing the COMMUTER and TRIMMS analysis programs. In addition, a survey was distributed to the I-526 Corridor stakeholders in conjunction with CARTA and Charleston County Economic Development to gauge the existing levels of TDM for area employers and willingness to implement TDM strategies in the future. From the responses received, the results of the survey indicated that more than 95% of the employees along the study area drive alone to work.

TDM options being considered include: Carpools/Rideshare Matching, Vanpools, Transit Pass Incentives, Telecommuting, Compressed Work Week, Work Flex Time, Staggered Work Hours, Bike/Walk Improvements.

Modal Strategies: The Modal strategy evaluation efforts have focused on how to improve and expand the existing transit system and potential strategies and challenges to shift truck trips away from the peak hours. The survey that was distributed to the I-526 Corridor stakeholders also provided valuable input for the modal evaluations, including the fact that the results showed that almost half of the employers in the area would be interested in transit if it was available to them.

Transit-related options being considered include: Modify/improve existing routes, Improved connectivity (shuttle service) to/from bus stops, Add/improve existing facilities and equipment, New transit routes, Public/Private Partnerships, Additional transit modes (BRT, Commuter Rail, Light Rail, etc.)

Freight-related options being considered include: Increase intermodal (rail) split, Extend operating hours for Port (and associated industries), Construct near terminal staging areas, Peak hour incentives/ disincentives, Create truck routes on primary/ secondary roads, Increase truck weight limits, Improve I-526 geometry to minimize car/truck speed differentials.

Traffic Operations: The Traffic Operations evaluation efforts have looked at a multitude of options, including restriping I-526 across the existing bridge structures to three lanes in each direction, interchange and ramp improvements, managed lanes, signing/wayfinding, pavement marking, signal optimization, and other geometric improvements.

The preliminary analysis shows that HOV and HOT lanes would not be appropriate for the corridor, due in part to I-526 being a circumferential freeway around Charleston with minimal directional splits of traffic throughout the day.

Capacity Improvement Capacity Improvement preferred alternates have been developed and evaluated for improvements to the I-526 mainline (widening to six lanes) and for the I-526 interchanges with Rivers Avenue, I-26, International Boulevard, Montague Avenue, Dorchester Road/Paramount Drive, Leeds Avenue, Paul Cantrell Boulevard, and US 17/Sam Rittenberg Boulevard.

The next steps for the project will include evaluation of the costs, benefits, and suitability of each of the different strategies, and developing performance measures and conducting environmental screenings for all strategies. After assuring the study's draft recommendations coordinate with other projects planned in and around the study area, the study team will schedule the last series of meetings with the Steering and Stakeholder Committees and a second public meeting with the general public.

October 2011 to March 2012:

Lots of valuable input was received from the general public at the September 20th public meeting. All of the comments received were collected and organized by how they addressed the four congestion management strategies: Travel Demand Management, Modal & Freight, Traffic Operations, and Capacity Improvements.

A two-day workshop with steering committee members and stakeholders in October examined the feasibility of every comment. With direction from the workshop input, the study team began analyzing the numerous improvement strategies and creating some preliminary concept plans for the corridor and its interchanges.

Particular issues of concern were the proximity of interchanges especially around the Interstate to Interstate Interchange at I-526 and I-26, the cost of widening bridges and elevated roadway over the area's marshlands, the length of acceleration and deceleration lanes, signage, and traffic signal coordination.

The study team's initial analysis of the strategies and the preliminary concept plans were brought back to the steering committee for their review at a February 2012 Steering Committee meeting before beginning traffic analysis on the most feasible options.

April 2011 to September 2011:

The Corridor Analysis for I-526 between North Charleston and West Ashley studied the current conditions of I-526 between US 17 in Charleston and Rivers Avenue in North Charleston. Data was collected on the Average Annual Daily Trips [PDF 6.88mb] along the corridor in each segment. Daily and hourly traffic counts were charted to understand peak hours (Ashley River [PDF 113kb] and Cooper River [PDF 114kb]) and peak months (Ashley River [PDF 153kb] and Cooper River [PDF 156kb]) in different directions. Incident information was collected to understand where accidents are occurring [PDF 1.34mb] and what type of accidents [PDF 115kb] are happening. Counts were taken of vehicle types [PDF 6.88mb] to understand the numbers of trucks versus cars traveling along the corridor. Traffic along the corridor was analyzed to see where people are getting on and off of the roadway coming from I-26 East [PDF 6.84mb], from I-26 West [PDF 6.85mb], from US 17 in West Ashley [PDF 6.85mb], and from the Cooper River [PDF 6.85mb]. All of this information was put into a computer modeling program to understand where the cars are on the roadway at peak times. Once the modeling program was completed, it could be used to begin testing the impact of traffic reduction ideas on the corridor.

Ideas on Travel Demand Management, Modal Strategies, Traffic Operations Strategies or Capacity Improvements were solicited from a variety of sources. These sources include a steering committee of implementers such as the municipalities, county, transit systems, and the Berkeley Charleston Dorchester Council of Governments; stakeholders who live or work along the corridor or care about transportation issues in general; attendees at a public meeting held on Tuesday, September 20, 2011 from 5:30 p.m. to 7:30 p.m. at the North Charleston City Hall; or comments gathered from our comment sheet, conversations with project staff, comment sections following media stories, or comments sent through this website.

A project team workshop will spend the next few months culling through the ideas received to date to prepare for testing them as potential congestion reduction solutions.

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