Weather Permitting, Signals Will Flash Yellow August 17;
​​Full Activation Mid-September

(August 16, 2021) – The Maryland Department of Transportation State Highway Administration (MDOT SHA) will activate ramp metering on 23 ramps along southbound I-270 in Montgomery and Frederick counties beginning on or about Tuesday, August 17, weather permitting. Crews will begin the process of activating the new system by turning signals at the end of the ramps to flashing yellow. Part of the I-270 Innovative Congestion Management (ICM) project, this is the next step in Maryland’s first ramp metering system.

“Our administration is committed to providing solutions to address congestion on I-270,” Governor Larry Hogan said. “Ramp metering is an innovative approach to reduce travel times, improve the quality of life for residents and spur economic growth in Frederick and Montgomery counties and across the National Capital Region.”

Ramp metering uses sensors that detect real-time traffic conditions and activate traffic signals, when needed, to more efficiently control traffic merging onto I-270. The system allows motorists to merge safely onto I-270 while minimizing delays and reducing congestion. When ramp metering is in operation:

  • Motorists will see a warning sign with flashing beacons.
  • When the beacons are activated, motorists should be prepared to stop at the stop line.
  • Once the signal turns green, drivers may proceed on the ramp and merge onto the highway.
  • The signal will allow one car at a time to enter the highway, optimizing traffic flow onto I-270.
  • Motorists are advised to use caution and reduce speeds approaching the traffic signal as there may be stopped vehicles waiting to merge onto the highway.

“Ramp metering is an innovative, cost-effective tool to improve safety, ease congestion and make daily commutes more reliable throughout the corridor,” MDOT Secretary Greg Slater said. “The system is new to Maryland, but in other parts of the country ramp metering is a proven tool that works to improve traffic flow and help drivers merge more safely and easily onto busy highways.”

Beginning August 17, crews will uncover and turn on signals to flashing yellow in stages along the 23 southbound locations. The flashing lights will alert motorists that activation of the ramp metering system is coming. The turn-on process will take about a week to complete, with groups of ramp signals being activated each day. Then, on or about September 15, crews will turn on the ramp metering system at all southbound ramps where the equipment is installed. The schedule is dependent upon weather. Additional reminders will be sent prior to September 15.

Ramp metering signals will have the capability to operate between 4 a.m. and 11 p.m. daily and are anticipated to be active during peak-traffic hours and when sensors detect congestion on I-270. The system also detects the length of vehicles in queue to help ensure ramps don’t back up onto arterial roadways. For more information and to view a location map and ramp metering video, click here.

In June, MDOT SHA tested the system on the ramp from northbound MD 118 to southbound I-270. The test allowed MDOT SHA to assess each aspect of the system in a live traffic environment. Crews monitored on-site and computer hardware and software components to ensure all worked correctly. In addition to the 23 southbound I-270 ramps being activated this week, MDOT SHA plans to install ramp metering on another 22 ramps onto northbound I-270 in 2022, for a total of 45 ramps at 18 interchanges by the end of next year.

Ramp metering is one piece of the I-270 ICM Project that Governor Hogan announced in 2016 to provide congestion relief and improved travel times throughout the 34.4-mile I-270 corridor from I-70 to I-495. Other elements of the overall $132 million I-270 ICM Project include additional auxiliary lanes between interchanges, extension of acceleration and deceleration lanes and reconfiguration and restriping of existing lanes to optimize traffic operations.

“Ramp metering, along with other ICM improvements, will help save drivers up to 30 minutes on their morning commutes between Frederick and the Capital Beltway,” said MDOT SHA Administrator Tim Smith. “Through the use of traffic signals and detectors, the system will not only balance demand and capacity on the highway, it also will mitigate backups on the arterial roadways.”

The I-270 ICM Project is separate from the New American Legion Bridge I-270 to I-70 Traffic Relief Plan. The ICM Project is aimed at helping improve today’s congestion by eliminating existing bottlenecks and adding intelligent traffic system that will improve reliability and predictability for today’s users. The New American Legion Bridge I-270 to I-70 Traffic Relief Plan will address long-term growth throughout the region. It will transform the corridor by moving more people and goods with less congestion and provide opportunities for rapid bus services, carpooling, new bicycle and pedestrian connections, and the option for single-occupant vehicles is to pay a toll when they need a faster, more reliable trip.

Phase 1 South: American Legion​ Bridge I-270 to I-370 proposes to replace the 60-year-old American Legion Bridge and provide two managed High Occupancy Toll (HOT) lanes from the bridge to I-270, and north on I-270 to I-370. Phase 1 North: I-370 to I-70, is in the pre-National Environmental Policy Act (NEPA) stage. While separate initiatives, the I-270 ICM Project and the New American Legion Bridge I-270 to I-70 Traffic Relief Plan would work in tandem as part of a multi-faceted traffic relief approach for the region. The I-270 ICM Project provides congestion relief and travel time savings along the I-270 corridor. The New American Legion Bridge I-270 to I-70 Traffic Relief Plan offers a public-private partnership to replace the aging bridge and provide new opportunities for transit and ridesharing, bike/pedestrian connections as well as congestion relief for the National Capital region.

MDOT SHA works hard to maintain safe traffic mobility in work zones for our crews as well as our customers. Drivers need to stay alert, focus on driving and look for reduced speed limits as well as other driving pattern changes. Please drive like you work here and slow down in construction zones.

For a list of all major MDOT SHA projects, go to Project Portal Visit our homepage at For a look at real-time traffic conditions, go to

Editor’s Note

Video and other materials related to the I-270 ICM Project are available upon request. Contact MDOT SHA Communications at 410-545-0303 or email