luggage take a taxi between the stations. It is possible to traverse the gap directly via the Orange Line from Back Bay Station to North Station, but it requires seven stops and not all of the southern lines pass through Back Bay; the Old Colony Lines, and Fairmount Line on the Commuter Rail do not. The Orange Line also provides a connection for Amtrak passengers who want to transfer between the Northeast Corridor and the Downeaster. However, North Station passengers add significantly to Orange Line congestion. Similarly, it is possible to connect between South Station and the Fitchburg Line via the Red Line at Porter station. Passengers on the Newburyport/Rockport Line can also take the Silver Line from Chelsea (Bellingham Square). The weekday-only MBTA bus #4 connects the two stations. The North–South Rail Link is proposed to fill all these awkward gaps in service, with direct connections requiring no transfers. 2018 NSRL feasibility study In June 2018, MassDOT released a North South Rail Link Feasibility Reassessment presentation that described several tunnel alternatives. The state began soliciting bids for a $2 million feasibility study on March 1, 2017. This study had been pushed for by the North-South Rail Link Working Group. The working group, NSRL supporters, includes Senator Ed Markey, Representatives Niki Tsongas and Katherine Clark, with Representative Seth Moulton leading the effort. It also includes more than half of Massachusetts mayors. Options The 2018 MassDOT feasibility study analyzed four possible options. Two options would run under the Central Artery (I-93), one option with two tracks and the other, more expensive, with four. The other two options, each with two tracks, would tunnel under downtown Boston several blocks west of the Artery. All the proposals connect the northern commuter rail lines with South Station and then to Back Bay and lines to the west. Only the four-track option would connect North Station with the Fairmount Line south of South Station. Under all the proposals, the Old Colony Lines would continue to terminate at the South Station surface platforms. The existing North Station and its surface platforms could be eliminated under all four options, making the area available for redevelopment. Central Artery four-track The most ambitious option is the only one that includes a new Central station (or Union Station) near its midpoint, and the only one with a rail tunnel connection to the Fairmount Line. North Station would be underground near