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MD 4/Suitland Parkway, Prince George's County, MD

A. Morton Thomas and Assoc., Inc. provided interchange design and traffic analysis for the MD 4 corridor and Suitland Parkway Interchange including a Value Engineering study of the interchange design developed in the planning process. AMT evaluated initial traffic volumes and modified for change in forecast year; analyzed the Suitland Parkway Interchange under several different scenarios including roundabout diamond interchange and flyover ramp and single point urban interchange; developed concept plans for two interchange designs, which included horizontal and vertical alignment, limits of disturbance, proposed right of way, braided ramps, roadway widening and access for industrial district.

Services included the following:

Capacity Analysis - Developed forecasted traffic volumes for the 2030 design year, utilized proposed development traffic numbers and MCOG traffic model to determine model constraints and destinations for AM and PM peak hourly volumes, analyzed intersections at ramps to determine the design year level of service, comparing two design interchanges. This interchange was analyzed as part of a corridor improvement project, improving three interchanges and the location of the project adjoining I-495 was a key element in the traffic model.

Access Studies - Analyzed the traffic destination to determine access and service road locations and volumes. Analyzed weaving movements and intersection storage requirements.

Geometry - Developed the preliminary design of two interchange configurations; flyover ramp with simple diamond interchange and Single Point Urban Interchange (SPUI). Utilized InRoads to design the horizontal and vertical alignments, centerlines, stationing, intersecting points and offsets. Verified proposed bridge clearances to meet minimum requirements.

R/W Determination - Performed drainage design, SWM and analyzed both interchange design grading to develop preliminary Right of Way documentation, utilized to develop cost estimate of property acquisition.

Maintenance of Traffic - Developed phasing concepts for preliminary design stage to determine additional costs to the project during the construction phase. Consideration of constructing the bridges and changing the grade of MD 4 to an underpass in excavation was a key factor in determining the phasing of this project.

Cost Estimate - Computed the cost estimate for constructing the interchange, service roads and corridor improvements for the Planning stage and Preliminary Design. Utilized current market value prices for construction materials and based unit prices on quantities. Estimated un-quantified items through a percentage base to ensure that all costs that would be itemized in the final estimate were accounted for in the preliminary estimate to determine the project budget.

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