WABA recently put together a detailed Concept Plan for the Arlington Boulevard Trail, with hopes that it will lead to more investment in the corridor and a complete and better trail. This is similar to the 1999 Concept Plan that WABA wrote for the Metropolitan Branch Trail (but hopefully will follow a faster timeline). Without rewriting the whole thing here, I'll just quote a bit of the summary.
Much of the Arlington Boulevard bicycle route already exists in the form of oﬀ-road paths and wide service roads with little traﬃc.Building just 1.3 miles of bridges and 8.1 miles of protected bicycle lanes (or oﬀ-road shared-use paths) would create a continuous trail,22 miles in length, on both the north and south sides of Arlington Boulevard. A basic, interim version of this focused on at-grade improvements and “low hanging fruit” could be built for just $2-4M,while a high quality path with grade separated crossing of major obstacles would cost $20-40M as redevelopment allows for increased investment.
The map below gives a pretty quick view of what is envisioned.
Mostly what is needed to bring this idea to fruition is paint, maintenance and some trail widening. The major capital improvements including a connection from the Marine Corps Memorial to the south span of the Roosevelt Bridge, new trail or protected bike facilities through the Seven Corners region, a bike/ped bridge over I-495,
It really is kind of a no-brainer. There are a lot of trails in the pipeline right now, but after that, there aren't that many options in the urban core. This is one of them.