Last week, GGW had a post that reported Arlington County's counter data for three of the six (I'm including Wilson here) bridges from Virginia to DC with bike/ped facilities.The three included were the 14th Street, Key and Roosevelt Bridges. Arlington doesn't have count data for the other three. Unsurprisingly, the Roosevelt Bridge had the lowest count. The Roosevelt Bridge has a lot of well noted and well known issues, but also a lot of potential that makes it low hanging fruit.
One thing that could be done relatively cheaply is to connect the downstream sidewalk to the Mt Vernon Trail via the Arlington Boulevard Bridge and at at-grade crossing ot the NB Parkway as seen in the crudely-drawn image below. I mentioned this before earlier this year.
The Arlington Blvd Bridge is oddly built, being ~twice as wide as the road, allowing the extra width to be used by a trail crossing.
An at-grade crossing of the Parkway would be odd, but there already is one further south, so it can't really be a deal-breaker.
From 23rd and Constitution, this is about 0.1 miles shorter for those going north on the MVT than using the Roosevelt Bridge's north side. So, it provides marginaly utility. But it would have a recreational benefit, especially if NPS were to add amenities to the two newly accessible medians between Arlingtlon Blvd and the Parkway. And it would create some redundancy as well.
For those going south from 23rd and Constitution it would still be about 0.2 miles longer than using Memorial Bridge, but it might involve less interaction with traffic. But the point is it could be done without building any new bridges. It would need NPS approval though.
A variation on this would create a TR bridge connection by going under Arlington Blvd at this same bridge, loop around and up to cross Boundary Channel on the south side of it, along S. Washington Blvd to an at-grade crossing of S. Washington Blvd and then up to the bike path along the north side of Memorial Circle.
This would actually have more utility to those who are going toward Arlington Cemetery or to Arlington via the trail along the west side of 110. But the space under the Boundary Channel Bridge is a bit narrow.
Then, if one wants to go completely nuts, there is this.
Instead of crossing Washington Boulvard it goes under Memorial Avenue on a protected bike lane (made by narrowing Washington Blvd) and then back over Boundary Channel via the unused west-side sidewalk on the Washington Blvd bridge, onto a trail along the inside of the loop there and then onto North Boundary Channel Drive. I have no idea who would use this. Still, no new bridges needed.