Environmental

I-495 & I-270 Managed Lanes Study

I-495 & I-270 Managed Lanes Study

I-495 & I-270 Managed Lanes Study

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Alternatives Retained for Detailed Study

Following the completion of additional traffic, financial and environmental analysis, MDOT SHA recommended that six of the Screened Alternatives, which included five build alternatives and the no build, presented at the Spring 2019 Public Workshops be carried forward as the Alternatives Retained for Detailed Study (ARDS) for detailed analysis in the Draft Environmental Impact Statement (DEIS).

Click each alternative in the chart below to view artistic renderings and descriptions that show how the build could work.

ards-title-update

You can also view the interactive online map that shows environmental features, community resources, details of the preliminary roadway layout, and preliminary limits of disturbance for each alternative as presented at the Spring 2019 workshops.

Other Alternatives Considered

Since that time, based on the Federal Highway Administration’s continued review of the traffic analysis completed for the Screened Alternatives and in review of new financial information, Alternative 5 is not considered a reasonable alternative to be retained for detailed study in the DEIS. Results of the traffic analysis showed that Alternative 5 would perform the worst of the build alternatives for most metrics used to evaluate existing traffic and long-term traffic growth and trip reliability, and would perform the worst among the Screened Alternatives in system-wide delay, corridor travel time, density/level of service and travel time (for general purpose lanes). However, Alternative 5 will be included in the DEIS for comparison purposes.

An additional alternative, the MD 200 (Intercounty Connector (ICC)) Diversion Alternative was also evaluated at the suggestion of Montgomery County officials and other agency stakeholders, which considered elements of the Montgomery County Regional Transportation Improvement Plan. The alternative proposed an alternate route for travelers to use MD 200 (ICC) instead of the top side of I-495 between I-270 and I-95 to avoid or reduce impacts to significant, regulated resources and residential relocations. The MD 200 (ICC) Diversion Alternative assumed no widening or new capacity on the top side of I-495 between I-270 and I-95, but did consider other potential less-impactful improvement options (known at Transportation System Management/Transportation Demand Management, or TSM/TDM, options), such as ramp metering and hard shoulder running, to attempt to relieve congestion.

MDOT SHA’s evaluation of the MD 200 (ICC) Diversion Alternative indicated that it would not meet the Study’s Purpose and Need of accommodating long-term traffic growth or enhancing trip reliability. The proposed TSM/TDM solutions on the top side of I-495 were either geometrically infeasible or would not provide substantial relief to accommodate long-term traffic needs. Also, the analysis indicated that MD 200 would not have sufficient spare capacity in the design year (2040) to draw enough traffic off I-495 to reduce congestion. As a result, the MD 200 (ICC) Diversion alternative would be projected to perform worse than all other Screened Alternatives in several key traffic metrics, including delay per vehicle, average speed in the general-purpose lanes, and level of service. On the top side of I-495 between I-270 and I-95, the MD 200 (ICC) Diversion Alternative is projected to perform worse than the no build. Therefore, the MD 200 (ICC) Diversion alternative cannot be carried forward. MDOT SHA will continue to work with our environmental agency partners to minimize impacts as much as possible on the remaining alternatives that meet the purpose and need.

Proposed I-495 and I-270 Managed Lane Access Locations

To evaluate environmental and traffic effects, MDOT SHA has assumed that the proposed managed lanes on I-495 and I-270 would be physically separated from the general-purpose lanes by a four-foot wide buffer space with plastic pylons. The pylons would be easy to remove and flexible enough to provide access for emergency vehicles to and from the managed lanes during incidents and emergencies. Drivers traveling in the general purpose lanes would be restricted from entering the managed lanes except at designated access points.

Several options to provide access to and from the proposed managed lanes are under consideration as a part of this Study. At this stage, access to and from the proposed managed lanes has been planned via direct access ramps and at-grade auxiliary speed-change lanes. These proposed access options and the locations on I-495 and I-270 are described below.

Direct Access

At locations along I-495 and I-270, direct (grade-separated) access ramps would carry managed lane traffic directly to and from major interchanges with other interstates and with the local street network.

Rendering example of a potential direct access interchange along I-495 or I-270.

Auxiliary Lane

Per the Guidelines for Implementing Managed Lanes developed by the National Cooperative Highway Research Program, an auxiliary speed-change lane allows a driver to enter into the managed lane facility by entering an at-grade ramp, traveling through the buffer, and then merging into the managed lane. The same scenario would apply for a driver leaving the managed lane facility to enter the general purpose lanes (National Academies of Sciences, Engineering, and Medicine, 2016).

Example at-grade access along I-495 or I-270. Not to scale.

Preliminary List of Direct Access Interchange Locations:

  • I-270 at I-370
  • I-270 at Gude Drive (to/from south only)
  • I-270 at Montrose Road
  • I-270 at Westlake Terrace (to/from north only)
  • I-270 at Democracy Boulevard
  • I-495 at George Washington Parkway
  • I-495 at MD 190/Cabin John Parkway
  • I-495 at I-270 West Spur
  • I-495 at MD 187
  • I-495 at I-270 East Spur
  • I-495 at MD 185
  • I-495 at US 29
  • I-495 at I-95
  • I-495 at US 1
  • I-95/I-495 at Cherrywood Lane/Greenbelt Metro
  • I-95/I-495 at Baltimore-Washington Parkway
  • I-95/I-495 at US 50
  • I-95/I-495 at Ritchie Marlboro Road
  • I-95/I-495 at MD 4
  • I-95/I-495 at MD 5

Preliminary List of Auxiliary Speed-Change Lane Locations:

  • I-270 East Spur south of MD 187
  • I-495 north of Clara Barton Parkway
  • I-495 west of MD 187
  • I-95/I-495 south of Baltimore-Washington Parkway
  • I-95/I-495 north of Ritchie Marlboro Road