Concrete Vein — sources and lineage

Boston’s Interstate network as built, scrubbed by the year each segment opened, against the network the 1955 Yellow Book planned. The two do not match, and the gap is the subject: the Inner Belt was never built, and the Southwest Expressway was stopped and its corridor turned over to transit.

Attribution required: Public domain (US federal government), Fair use.

Sources used

• General Location of National System of Interstate Highways ("Yellow Book"), 1955 — Boston plate Public domain (US federal government)

  The planned network, digitised from the georeferenced plate (p. 37). This layer contains only what the 1955 drawing shows; everything about why a route was not built is a later event and is carried by an epoch chip instead.

• National Highway Planning Network (NHPN / NTAD) Public domain

  Built limited-access centrelines, clipped to the Boston metro inside MA-128.

• History Cambridge — Inner Belt chronology Fair use

  Secondary chronology used to date segments and to establish the Inner Belt cancellation sequence. Cited per segment in the open-year table.

How complete this is

• Boston Interstate centreline miles: 100.0% dated, 0.0 explicitly unknown of 100.0.

Sources deliberately not used

• Harvard Dataverse 10.7910/DVN/UMLWGW

  A CC0 census-tract replication package for Chicago and Detroit. It is not a segment-level map spine for Boston, and using it as one would misrepresent both its geography and its unit of analysis.

• jeffrlin/freeway-data 1947 plan

  The 1947 plan is an intercity network. Substituting it for the 1955 Yellow Book urban plates would put the wrong lines on the map under the right label — the specific error this product exists to avoid making about planned routes.

• Any default open year for undated segments

  A segment with no located source is recorded as unknown, with the reason, and counts against coverage. A map where every road has a date would look more authoritative and be less true.

Prior art

• The Sargent moratorium, the hearings and the revolt are policy events of the late 1960s and early 1970s. They are shown as epoch chips with their own citations, never as attributes of a 1955 drawing.
• The Southwest Expressway is recorded as planned-partial-or-diverted rather than simply unbuilt: the corridor exists and carries transit, and flattening that to "vanished" would erase what actually happened to it.