This fall's tie replacement project is on track 2 between Boston and Southboro. Track 2 is the track used for both inbound and outbound rush hour trains between Boston and Framingham.
The tie replacement project is necessary maintenance and actually decreases the risk that restrictive speed limits will be imposed due to track and railbed condition. Every 6 months, an inspection train checks the condition of the tracks. This sophisticated "geometry train" uses a number of sensors to verify that the track and railbed are safe for the operation of the railroad at the highest possible speeds (daily inspections check for visual and other defects). If the geometry train detects a fault, there is a speed restriction imposed on that section of track until the defect can be repaired. Without regular replacement of ties and resurfacing of the railbed, the risk increases that the geometry train will find defects that will result in temporary speed restrictions.
As many of you recall, the previous major tie replacement project in May-June on track 1 resulted in significant delays for many trains. The MBTA & Keolis changed the way the current tie replacement project is being executed for track 2 in order to minimize delays.
The disturbance of the railbed from any construction work requires temporary speed restrictions after the work has been done. But how the work is sequenced can affect the length (distance) of those speed limits - and by minimizing the length of the speed limits, the overall impact to on-time performance can be mitigated.
For this fall's project, the productivity of the construction has been intentionally slowed down in order to minimize the length of the temporary speed restriction. In addition, a specialized piece of equipment - a track stabilizer - has been added to the track surfacing crew so that the speed restrictions can be further minimized.
For this tie replacement project, the sequence is:
1) close track
2) tie replacement crew / work
3) track surfacing crew / work
4) open track
5) temporary speed restriction for first / ONE train movement across entire length of work area (both tie replacement area & surface work area).
6) ~24 hour 30 mph temporary speed restriction for the ~1 mile of track that the tie replacement crew disturbed (or actually the disturbed area where the surface crew HASN'T worked yet).
The 'track surfacing' work is the distribution of new ballast (stone) and the tamping and stabilization of the stone. Normally the area where the surfacing crew works requires a temporary speed restriction for 24 hours. Adding the stabilizer to the surfacing crew reduces the temporary speed restriction from 24 hours to one train passage.
In addition to adding the track stabilizer to the surfacing crew, the tie replacement crew's productivity is being intentionally limited so that they do not get too far ahead of the surface crew. Normally, the productivity of the tie replacement crew is HIGHER than the surfacing crew. So over time (multiple days), the tie replacement crew could get way ahead of the surface crew, resulting in a 24 hour temporary speed restriction for their work area and the entire 'gap' between the two work areas.
In other words, for this project, the tie replacement crew is not allowed to go as far as they could if they were unconstrained. This limits the tie replacement crew to probably ~75% of their unconstrained productivity.
An MBTA manager mentioned to me that they can remember an instance when the Old Colony lines had tie replacement done and the temporary speed restriction between the crews got all the way up to 7 miles. This was a long time ago - but that is a long distance to be restricted to 30 mph.
The track stabilizer as a member of the surfacing gang and the constraint on the tie replacement crew were both NOT present during May-June when they worked on track 1. The delays resulting from having multiple miles of temporary speed restrictions were catastrophic to on-time performance for that period - and not only were there many delays, but the delays were much more substantial than the delays being caused by this fall's tie replacement project.
The overall scope of this tie replacement project is from Boston (actually CP 4 on the west side of Boston Landing station) to CP 28 in Southboro (see the map). 33,000 ties are scheduled to be replaced - an average of 1,600 per mile. That's about half the ties (US railroads typically have ~3,000 ties per mile).
As of today, the work has been completed from CP 4 in Boston to just west of Wellesley Farms station. Railbed construction and maintenance is usually halted in the winter when the ground freezes. This project got a slightly later start than was intended - I think it started around the beginning of October. The current plan is to continue with the project until approximately December 16th, with the remainder of the work presumably deferred until the spring.
The limitations on the track work productivity have been successful and have resulted in 24-hour 30 mph speed restrictions of no more than one mile since the project started in October. Many of you have commented on the recent "slow-downs" in Wellesley and Newton - and this is what you have been noticing. It is much more noticeable on an express train that would be operating at 60 mph for that whole stretch - a one mile speed restriction requires slowing down before the train reaches the start of the speed restriction (as opposed to a local train that may never even get up to 60 mph after its nearest station stop).
It is likely that this tie replacement project has had a impact on on-time performance for many trains over the past month. As noted, a one mile speed restriction for an express train may be enough to push it close to 5 minutes late (the threshold for "on-time"). In addition to the impact on rush hour trains, there have been more significant delays for mid-day trains when one track is out-of-service completely and train service is limited to one track only during the construction.
So in summary, we need to give credit where credit is due. I'm not suggesting that ~60% on-time performance is acceptable - but I am suggesting that without these changes to the way the tie replacement project is being executed, the delays related to the tie replacement project would have been much more extensive.