Workers for Concrete General excavate dirt to provide proper slopes for the road.
(MDOT SHA and Concrete General photo)
Maryland's I-270 travels through the busy communities of Frederick, Germantown, Gaithersburg and Rockville to the D.C. metropolitan area. This corridor occupies two lanes in each direction before expanding to seven lanes as it nears I-495, the beltway that circles Washington, D.C. I-270 is one of the busiest roads in Maryland.
Often the best excuse for being late to work, school or an activity is simply "270."
Traffic planners at the Maryland Department of Transportation State Highway Administration (MDOT SHA) decided to change that conversation by putting their heads together with Concrete General Inc. in a Progressive Design-Build Project. The object of the job is to reduce travel time congestion headaches for commuters. The team is attempting to reduce congestion and increase safety without widening the freeway in either direction.
The total project investment is about $132 million and is 85 percent complete.
Besides the 12 locations where geometric improvements have been designed and constructed, the design-build team is installing a new ramp metering system at 22 northbound and 23 southbound entrance ramps along the nearly 30-mi. I-270 between Frederick and I-495.
Flashing yellow and green signals on the ramps will tell drivers when the best time to merge with traffic. This ramp metering system times traffic merges to better regulate the flow without causing major traffic back-ups on the roads entering onto I-270. Downstream Traffic Sensors will monitor real-time traffic conditions and help control traffic merges more efficiently. The signals are timed so just one car at a time is allowed to enter from each lane.
The MDOT team is led by Steve McVeigh, MDOT SHA construction project engineer, and Sean Campion, chief, of the MDOT's Innovative Contracting Division.
In some locations, removing existing pavement markings and installing new pavement markings allowed for an additional travel lane using the existing roadway footprint. The work has required more than 25,000 tons of asphalt for resurfacing and reconstructing the existing lanes.
The project involved some complex working relationships.
"The entire project stretched 33 miles," said McVeigh. "It involved six construction packages and a total of 16 different projects. We had to think outside of the box in order to creatively work with multiple crews and multiple inspectors at all times."
The work team gave commuters a chance to test out the ramp metering system, before making it fully operational.
"We turned on the system on a northbound ramp of 270 during normal traffic first," said McVeigh. "We didn't want to activate it during commuting time. We are going to let people get used to it first before turning it on from 5 a.m. to 11 p.m."
Mike Higgins, Concrete General's design-build project manager, also praised the cooperation that occurred for the progressive design build team.
"MDOT SHA came up with a simple concept: what can you do to move the most traffic in the shortest time through the I-270 corridor within a fixed budget? That opened us up to consider many possibilities."
The Concrete General-led design-build team included RK&K, a Baltimore-based engineering firm who was responsible for the design, and Bruce & Merrilees Electric Company, a New Castle, Pa.-based firm who was responsible for construction of the ramp metering for the project. This I-270 Innovative Congestion Management project is the first time ramp metering has been used in Maryland.
"Ramp metering is a type of active traffic management, which manages the flow of merging traffic to make it more orderly and efficient," said Higgins. "It eliminates most of the drivers who cut into traffic as quickly as possible and usually creates more congestion. Implementation of this active traffic management technique lengthened some merge lanes and added additional queue areas on some ramps. The ramp metering also used messaging to assist motorists on the entrance ramps for entering the traffic flow on I-270 more efficiently.
"We looked at both entrance and exit ramps for each of the interchanges from a traffic volume and crash data standpoint and were able to make minor modifications to the existing traffic movements to reduce congestion and improve throughput," said Higgins. "We were also able to modify existing entry and exit points that changed the traffic flow that had been the source of numerous accidents in the past. Of course, nothing fouls up traffic like accidents."
Higgins believes this creative thinking resulted in some sizeable savings.
"We did not have to widen the existing footprint of I-270 except in small areas," he said. "That meant fewer utility relocations and fewer environmental impacts were required for the work. That along with the time savings for commuters from these improvements has resulted in a successful project for both the state and Maryland drivers." CEG
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