The Office of Transportation Planning's GIS Services group maintains many transportation related GIS layers.
Layers include road, rail, water, and air transportation modes maintained by the Massachusetts Department of Transportation. In addition, transportation agency jurisdictional boundaries are available. All of these layers can be found at our new Open Data Portal which allows you you use and download the data in multiple formats.
All of the GIS layers are stored in NAD 1983 Massachusetts Mainland State Plane Coordinates - Meters.
Any other data layers that are not maintained by MassDOT can be found at the MassGIS website.