I concur with Tom Wright’s comment: the specifics from the county's approved plan are essential to the argument against connecting Calverton Drive through to Dean Drive (discussed on pp. 33 of the final draft study, on fixing broken links).
Technical Memo I summarizing results from the 2010 traffic study and other available data does not indicate any measurement of impacts from extending Calverton Drive to create a connection with Dean Drive. I understand that the recommendation now is to carry out a feasibility study. The rationale offered in the final draft of the Hyattsville Transportation Study (Sept. 26, 2018) for eliminating one-way streets and connecting Calverton as a through-street (building a connected street network) is “to distribute traffic more equitably and improve the quality of life of the residents” (pp. 23). This sounds good, but firstly, not all streets are equal in construction or planning so that they will sustain even moderate traffic without serious compromises (is Calverton Drive equal to Adelphi Road? To Belcrest Road?), and second, there is no measuring quality of life or equitable distribution of traffic in a study like this. This recommendation ultimately seems to be rooted in the authors’ affection for grids, despite acknowledging the fact that building more roads is not a sustainable solution to traffic problems (pp. 25, the notion of “induced traffic”, more roads means more traffic, generally, and this is irresolvable).
Calverton does not have sidewalks beyond the portion of the subdivision constructed during the 1950s. It is arguable (in that neighbors argued about it) that Calverton does not need sidewalks. Rosemary Terrace was designed as automobile-oriented suburban housing, with a combination of relatively low housing density, off-street parking, and streets wide enough to accommodate local, low-speed traffic alongside pedestrians and cyclists. The design works today but would be compromised by turning Calverton into a through-street. It would require provisions for serious improvements in safety, now made necessary by potential new traffic on neighborhood streets.
I have a problem with the idea that Calverton is a broken link. Rosemary Terrace has a design; Calverton is part of that design and Calverton goes exactly where it needs to go. I have a problem with the idea that all streets should be through-streets and that good planning will create a grid, and that grids minimize traffic. The notion that all streets should be through-streets is simply arbitrary. I don't think that is a very current planning ideal, and the study holds it up as a guiding principle. To create (unmeasured!) negative affects in neighborhoods for the sake of an abstract idea about how great street grids are is not defensible.
Improvement in connectivity between Calverton and Dean Drive via walking or cycling, yes do it. There are already informal footpaths across private property providing this connection. Formalize them, buy the right-of-way to establish a safe, appropriately lighted non-motor vehicle access that is passable to emergency vehicles but does not siphon automobile traffic down Calverton Drive. This is a sustainable alternative. If induction of traffic applies to pedestrians and cyclists, please do induce more pedestrian and cycling traffic down Calverton.
The intersection of Adelphi and Wells needs help desperately. Try and cross Adelphi on foot within the time permitted by the light. Try and cross with a stroller. Try and make a left turn at that intersection on a bicycle. I understand the study is constrained by what the City of Hyattsville can and cannot do. But a study like this can and should document such a problem and a hazard, so that agents pushing the SHA to address the problem have something concrete, a published source to point to.