 Construction of Exit 4A, to be located approximately a mile north of Exit 4 in Londonderry, was slated to begin construction in late 2020.Exits 17, 19, 21, and 25 in Massachusetts were eliminated as part of the Big Dig.Massachusetts exit numbers were to be changed to those based on I-93 mileposts with a project that was due to start in early 2016, but this project was postponed by the MassDOT for several years.