395 - GSA Development of St. Elizabeths Campus

The other constructability issues relate to construction of retaining walls and roadways for thedirect connection access road to St Elizabeths. If this work is to be constructed in a final buildout phase, access and construction will be difficult since it is located between and above activeroadways creating a tight work area and a linear construction operation.Design Exceptions for West Bound to North Bound Loop Ramp:The Alternative 2 Modified meets AASHTO standards for this ramp, therefore no designexceptions are required.Safety Impacts of Design:The existing loop ramp configuration at the interchange has three safety concerns.1. The low speed (15 mph) on the Off Ramp requires the motorists exiting from the 45mph I-295 to reduce speed in a short distance in order to safely make the turn on thetight-radius loop ramp, therefore potentially creates high risk of off-road and overturncrashes;2. Drivers from the On Ramp have to speed up from 15 mph to 45 mph while looking foracceptable gaps to merge into the freeway traffic, and this could cause high risk for sideswipeor read-end crashes;3. The short weaving area (approximately 280 feet) between the On Ramp and Off Rampfurther complicates the vehicle interactions and creates a difficult driving environmentfor the motorists, also increasing the risk of side swipe and rear end crashes.The Interchange Alternative 2 Modified mitigates the three above concerns:- Eliminates the Off Ramp loop by building a separate downstream exit. This exitprovides a higher design speed and longer decelerating distance, therefore mitigatingthe currently demanding speed reduction and eliminating interaction with othervehicular movements.- Eliminates the On Ramp loop by building a C-D road, which features a much longerdistance for motorists to accelerate and merge into the mainline I-295.- Completely separates the On Ramp and Off Ramp so that there will be no weavingbetween the two movements. As a result, all the alternatives will potentially resolve thesafety concerns and provide a more comfortable driving situation for the motorists.Traffic operation analysis for Alternative 2 Modified was performed and the results areprovided in Section 5.5 of this document.2.4.4 No Action AlternativeThe No Action Alternative assumes that DHS consolidation and relocation to St. Elizabeths doesoccur; however, only minimal roadway improvements providing access to St. Elizabeths isassumed. Specific modifications to the surrounding network are described below:• Construction of a north-south three-lane arterial called the West Access Road to providevehicle and pedestrian connections from Firth Sterling Avenue to Gate 4 of the West2-13