A few quick comments:
- I think the curvature of tracks only plays a rather small part of travel speed, especially if the curve is also relatively gentle like those on the 57 (which can be done theoretically with TBMs). If anything, the number of stops matters a lot more for travel speed.
- In many cases, the time savings from a more direct route gets eliminated by the extra time it takes to get to the station in the first place. (This alone does not speak against a B&A routing entirely, but it does play a part.)
Comparing the travel times for the Orange Line from Roxbury Crossing to Back Bay, gives a
travel time of 4.5 minutes to go 3 stops (1.5 miles, 2.5 km). The E branch of the Green Line, which runs on street level in dedicated lanes from Brigham Circle to Copley, takes 9.4 minutes from LMA to Copley, 1.6 miles (2.7 km). A similar distance, but twice as long on the Green Line E branch than the Orange Line, with 5 stops instead of 3. (
Brigham Circle is 11.3 mins, but 1.9 mi, 3.1km). Even during off peak hours, it still takes 9.8 minutes to travel from Brigham Circle to Copley in late nights and early mornings with minimal traffic.
Even with a Huntington Ave Subway extension from Symphony to Brigham Circle, plus elimination of the Northeastern and Prudential stops, it still would be slower to ride the Huntington Ave. Subway from Brigham Circle to Copley, than the equivalent trip from Roxbury Crossing to Back Bay on the Orange. Removing Prudential and Northeastern stops might save 2 minutes of travel time, plus 1-2 minute off peak/3-4 minute peak periods of street running shifted underground and removal of 10 mph/16kmh at switches. The end result being 7 - 8 minutes from Brigham Circle (6 minutes from LMA) to Copley on the Huntington Line, compared with 4.6 minutes from Roxbury Crossing to Back Bay on the Orange.
I suppose the Huntington Ave. Subway would need conversion from LRT to proper HRT (assuming the curves are slightly smoothed to meet the Harvard Curve's turning radii), but even then, following the exact Green Line routing to Copley would still likely be slower from the equivalent GL stops, versus the OL stops at Roxbury Crossing/Ruggles.
Roxbury Crossing to Chinatown on the OL is 8 minutes, I not sure how it would be possible, even with a HRT Green Line from Boylston to LMA, can also take 8 minutes, despite having the same # of stops after removal of the NEU/Pru stops.
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Having more circuitous routes would still hurt legibility of the transit system and it's attractiveness (and hurt the viability of bringing HRT west of Newton Corner). In addition, bus routes can easily be reconfigured to bring riders to the train stations (hence why stop spacing on the B & A would be needed for connections with existing bus routes; to push riders from the 57 and onto rapid transit). It's also worth noting that
Boston Landing station and its TOD has very little transit connectivity with other local bus routes today.
- Increase frequency on the 86/65 buses to every 8 - 9 min peak/12 - 14 min off peak, gain frequent crosstown connections to 3 RTL lines.
- Extend the 65 from Brighton Center to Brighton Depot/Boston Landing, more than doubling bus service from Brighton Center to Brighton Depot + bringing bus connections to Boston Landing's TOD.
- Eliminate the Union Sq. detour on the 66 bus and stay on Harvard Ave. to bring riders directly to the Allston Depot station on the B & A.,
- Reroute the 64 to Brighton Center, adding additional RTL connections to Central Sq. in Cambridge.
Finally, if bus service on Brighton Ave., is removed, and the B & A subsituting the 57 in Allston, it could make room for dedicated bike paths, as the 57 corridor lacks good cycling routes that take the shortest path downtown (which is today's 57 bus, which is the shortest route by cycling). The Charles River cycle path is closer to much of the B & A route, especially near Oak Sq. and Brighton, and east of Packards Corner, but leaves most of Allston Village and Union Sq. without a cycling connection.
Today, a trip from Brighton Center to Downtown at 8AM rush hour takes
47 minutes on the 501. A 2 seat ride on the 57 and the Green Line, often unreliable to due traffic congestion, bunching, transfers, and delays, takes a minimum of 40-45 minutes if not more. A RTL line following the B & A routing (with all stops) would take approx ~25 minutes from Newton Corner to downtown, and ~21 minutes from Brighton Depot. Assume 6 minute headways on the B & A, and the 86 and 65 running the aformentioned frequencies, for a combined headway of every 4 - 6 minutes, for the 4 minute bus trip from Brighton Center to Brighton Depot. This means that a full trip from Brighton Center to downtown, with a transfer at Brighton Depot to the B & A mainline, would take ~
38 minutes at most, 10 minutes faster than the 501 today (20% faster), and still faster than the 57 bus + GL. If the transfer times are short, it is still possible to complete this trip in as little as a halff hour from Brighton Center (Washington St & Chestnut Hill Ave).
Any rail station that gets built in Newton Corner would likely cause the removal and the end of today's express buses. If Watertown doesn't get a branch off Newton Corner, or if a
transfer is required to reach Back Bay, it would result in today's one seat ride on the 504 into one with two transfers.