[bike] Touring the commuter rail system

Wound up biking alone yesterday, after a three-week break. I didn't feel like doing a lot of planning, but the bike map suggests that it's possible to bike happily outside of 128 from Braintree to Waltham, so I headed out through Brookline with an eye for getting to the Blue Hills, maybe aiming for 50ish miles with some hills thrown in.

It's worth noting that the greater Jamaica Pond area is hillier than one might think from just driving around there. Also, that one should get their directions straight if they're trying to avoid the Arborway/Centre St intersection.

Left to my own, I made it 47 miles, going via Readville, out on 138 without doing anything particularly interesting in the Blue Hills, then clockwise back to Needham, at which point I headed back inbound, picking up 16 in Needham. I wound up taking a reasonably detailed tour of every commuter rail stop I passed, except for Norwood Center. I must have worn myself out early, along with being somewhat out of shape, since (especially right after lunch in Canton) I was trying hard to judge where exactly I should turn back and deciding if I really did have 10-15 miles left. If I wasn't right between trains I probably would have punted at Needham Junction.

Route map (since it's GPS now, you get to see all of the train-oriented noodling around); pictures (all of train stuff).

What's up at Needham Heights?

Here we're in "technical train question" territory, complete with ASCII art. Yesterday I was bumming around the Needham Heights commuter rail station. It's the end of the (largely single-track) Needham commuter rail line; that line runs north-and-south here, but northbound, the direction more towards Boston ("physical-inbound"), is the opposite direction from the way commuter trains to Boston actually go ("logical-inbound"). I suspect there's also some freight traffic, continuing physical-inbound across 128 into outer Newton industrial land. It looks like this:

-- To yard ----------\   (3)                 (4)(5)
-- To Boston ---------\------------------------------ To Newton ---
                 (1) (2) *** Platform ***    (4)

(1) is a three-head color-light signal, except it only has lights to show "stop" (red-red-red), "approach" (yellow-red-red), or "restricting" (red-red-yellow). (2) is a hand-thrown switch. (3) is what I'll call the "magic signal box"; it'd be on the right-hand side of a logical-inbound train at cab height. (4) are signs saying "END ABS" for logical-outbound trains. (5) is a single-head color-light signal with only red and yellow lights.

My GIMP foo is not good enough to get a non-garish picture of the magic signal box, but see here and here. It has, in four separate columns, position-light aspects for "clear", "approach medium", "approach", and "restricting", plus a red button.

If I was going to guess at this, I'd guess there would be an interlocking (0) off the left side of above. Logical-outbound trains would get a yellow signal there, taking them through the "END ABS" sign (4). Freight trains proceeding further (the right-of-way does look to be maintained) would have special clearance. Logical-inbound trains would get a red or yellow signal at (5) depending on whether the platform block is occupied or not, and the signal at (1) is either "enter yard" or "proceed on main line" depending on the switch (2). The "BEGIN ABS" sign is probably at (0). The box at (3) can be used by commuter train operators; if they press the button, the box lights up, showing "restricting" if the switch is set for the yard and otherwise repeating the signal aspect at (0). But this is all speculation.