Quick Note: Timed Orbital Buses

Outside a city core with very high frequency of transit, say 8 minutes or better, bus and train services must be timetabled to meet each other with short connections as far as possible. Normally, this is done through setting up nodes at major suburban centers where trains and buses can all interchange. For example, see this post from six months ago about the TransitMatters proposal for trains between Boston and Worcester: on the hour every half hour, trains in both directions serve Framingham, which is the center for a small suburban bus system, and the buses should likewise run every half hour and meet with the trains in both directions.

This is a dendritic system, in which there is a clear hierarchy not just of buses and trains, but also of bus stops and train stations. Under the above system, every part of the Framingham area is connected by bus to the Framingham train station, and Framingham is then connected to the rest of Eastern New England via Downtown Boston. This is the easiest way to set up timed rail-bus connections: each individual rail line is planned around takt and symmetry such that the most important nodes can have easy timed bus connections, and then the buses are planned around the distinguished nodes.

However, there’s another way of doing this: a bus can connect two distinct nodes, on two different lines. The map I drew for a New England high- and low-speed rail has an orbital railroad doing this, connecting Providence, Worcester, and Fitchburg. Providence, as the second largest city center in New England, supplies such rail connections, including also a line going east toward Fall River and New Bedford, not depicted on the map as it requires extensive new construction in Downtown Providence, East Providence, and points east. But more commonly, a connection between two smaller nodes than Providence would be by bus.

The orbital bus is not easy to plan. It has to have timed connections at both ends, which imposes operational constraints on two distinct regional rail lines. To constrain planning even further, the bus itself has to work with its own takt – if it runs every half hour, it had better take an integer multiple of 15 minutes minus a short turnaround time to connect the two nodes.

It is also not common for two suburban stations on two distinct lines to lie on the same arterial road, at the correct distance from each other. For example, South Attleboro and Valley Falls are at a decent distance, if on the short side, but the route between them is circuitous and it would be far easier to try to set up a reverse-direction timed transfer at Central Falls for an all-rail route. The ideal distance for a 15-minute route is around 5-6 km; bus speeds in suburbia are fairly high when the buses run in straight lines, and if the density is so high that 5-6 km is too long for 15 minutes, then there’s probably enough density for much higher frequency than every half hour.

The upshot is that connections between two nodes are valuable, especially for people in the middle who then get easy service to two different rail lines, but uncommon. Brockton supplies a few, going west to Stoughton and east to Whitman and Abington. But the route to Stoughton is at 8.5 km a bit too long for 15 minutes – perhaps turning it into a 30-minute route, either with slightly longer connections or with a detour to Westgate (which the buses already take today), would be the most efficient. The routes to Whitman and Abington are 7 km long, which is feasible at the low density in between, but then timetabling the trains to set up knots at both Brockton and Abington/Whitman is not easy; Brockton is an easy node, but then since the Plymouth and Middleborough Lines are branches of the same system, their schedules are intertwined, and if Abington and Whitman are served 15 minutes away from Brockton then schedule constraints elsewhere lengthen turnaround times and require one additional trainset than if they are not nodes and buses can’t have timed connections at both ends.

Planners then have to keep looking for such orbital bus opportunities. There aren’t many, and there are many near-misses, but when they exist, they’re useful at creating an everywhere-to-everywhere network. It is even valuable to plan the trains accordingly provided other constraints are not violated, such as the above issue of the turnaround times on the Old Colony Lines.


    • Alon Levy

      Where do they connect? There isn’t any regional rail in Vancouver, SkyTrain runs way more frequently than that and West Coast Express only runs at rush hour.

  1. Nilo

    Harlem Ave in the Chicago are looks almost perfect for this. Though maybe it would be improved if the Metra stations were slightly moved. North of the Chicago River from North to South there is the BNSF Line, Blue Line Congress Branch, Oak Park Green Line/UP-W station, Milwaukee West (though the station is two blocks off the Ave), Blue Line O’Hare Branch, and UP-NW line. Though the UP-NW basically has two stations equidistant from the Avenue. There are additional Metra stations well north and south, but I suspect the bus line would getting too long at that point.

    • Fbfree

      Harlem has fairly high density and already has more frequent buses (albeit split between two agencies and multiple short-turns). This would apply more to Lagrange Road between Lagrange and Rosemont. York Rd from Hinsdale to Mt. Prospect would be another similar route (Pace bus 330) with a currently schedules 19 minute gap between the BNSF line and UP-W, and a further 11-12 minute gap to the MD-W.

  2. Max Wyss

    It can be really tricky setting up such schedules.

    The best is if these buses connect nodes, because that allows for a driving time of maybe 23 minutes. If it is more, the slightest disturbance can make connections to be missed.

    The ZVV has several such lines between the Lake Zürich and Uster/Wetzikon, and they are doing their best to get connections. What may suffer, however, are bus-to-bus connections with -1 minute changing times…

    But such issues also concern local feeders, if their line is just too long; again, for a main node of the superior network, the round trip should not take more than 23 minutes.

  3. Kristian

    The CircleRoute in Perth, Australia, does this reasonably well. It is a circumferential route in the middle-ring suburbs connecting all 6 of the suburban rail lines, with minimum all day frequency of 15 mins (equal to the minimum rail frequency) Connections are well timed.

  4. Nathanael

    I think they’re trying a few in the Toronto suburbs. The radial rail lines to the west intersect grid-like north-south roads.

  5. FDW

    A good example of such an orbital route in a San Francisco context would be the 44 O’shaughnessy. If San Francisco had a proper radial subwas, it would connect to all of them. Another example, in a Seattle context would be the 560, which will eventually connect with 4 of Seattles radial corridors.

    • Alon Levy

      If SF had proper radial subways, they’d run every 4 minutes, so there wouldn’t be much point in timed connections. This is specifically something for suburban buses.

      • FDW

        I’d agree with you on that in SF, and the one that do exist RN were providing that level of frequency pre-covid. The 560 in Seattle is more like what you’re describing: it connects West Seattle to Bellevue via Burien, Sea-Tac, Renton, and I-405. It connects to Cental Link, and will connect to East Link and West Seattle Link in the future, and Sound Transit is planning on major upgrades for its corridor in the near future. Of note, the 560 is one of the routes Sound Transit took from Metro, and its predecessor went all the way up I-405 to serve Bothell, Kenmore and Shoreline.

  6. F-Line to Dudley

    Brockton bus coordination with adjoining rail lines is mainly limited by which town are full- vs. partial/barely dues-paying members of the BAT bus district. Stoughton’s a full member, so the #14 gets par schedule slate to any of the intra-Brockton locals. The Westgate Mall sojurn, which I’m very familiar with, is a bit too meandering and could be streamlined significantly for less clock chew. But other than that it’s a pretty damn good, taut, and very well-patronized route. By legacy quirk of BAT’s ancient lineage as a street railway the Ashmont bus through Avon/Randolph is full-scheduled (and actually beats the pants off M’boro Line commuter rail on the midday off-peak when train schedules are uselessly gapped out but the buses make great time in very little MA 28 traffic). Though Asmont’s got some weird legacy cruft in stop selection where it overlaps the MBTA bus district. It ends up easier to ride the whole way into Ashmont than try to catch the Mattapan trolley in Milton because of paper barriers sometimes/inconsistently enforced.

    Polar opposite famine story when you’re talking Abington, which only subsidizes barest tokenism bus service. The local out of downtown turns at the Walmart parking lot a few feet over the Abington town line; it’s functionally just another intra-Brockton bus. Shame because the #5 is one of the most heavily-patronized of all for hitting the big hospital right before the town line. The Rockland Flex only runs 7 daily round-trips to 4 stops in Abington/Rockland requiring a transfer from the #5 local at either Brockton Hospital or Walmart because Flex doesn’t even run to downtown. Plymouth Line linkage is thus functionally nonexistent because Abington won’t even pay in enough to run their near-useless bus in the extra 2 miles to BAT Center. Nothing whatsoever touches Whitman. West Bridgewater and Bridgewater are well-covered by campus shuttles that the general public can ride easily enough, but since Bridgewater State U. is the one ponying up for the subsidy and not the towns the integration with BAT is coincidental at best. Those routes should be full-on folded into the BAT system. Moreover, I think you’ve got a great case for reinstating the North Abington stop on the Plymouth Line that the state passed over in the ’97 restoration because there’s 2 intracity BAT routes (#10 and #11) that can easily be reshaped or augmented to shoot full service down Chestnut St. over the 3-mile straight line to that density-serving stop location. But you need to first solve for Abington’s meager self-funding capability.

    This is where advocacy for MassDOT to pump bigger across-board investment into the outlying RTA bus districts is going to be a key outflow plank in Regional Rail-ification. BAT’s system layout is spot-on ideal for tightly spanning full service between the Middleboro Line @ BAT Centra, Plymouth Line to east, and Stoughton Line (including South Coast Rail Phase II extension or installment plans therein hitting Easton) to West. The core system already has useful frequency threshold, tight schedule adherence, and geographically well-spread spider map for extension across town lines. But you’re never going to get Abington, Whitman, or the Bridgewaterses full-service coverage as strictly municipal pay-ins. They’re too much starkly smaller and more financially constrained than Brockton and Stoughton, and inertia is a bitch across the urban vs. rural divide that still shapes those towns. State-catalyst makeover of the RTA’s would really help a lot to get things moving by applying top-down assistance at easing the subsidy gradations between towns, especially BAT which is one of the most readily expandable districts already on the map. Though you could point to similar examples all over Eastern MA at the major multimodal intersections with Regional Rail.

    Maybe even some potential to birth all-new RTA’s. For example, local routes out of Salem really suffer on achievable service levels being tied to the Lynn Bus Terminal equipment pipe. The 400-series routes out of Lynn have all for 41 years since the T acquired the ex- Eastern Mass Street Railway bus district been forced to do a taffy-stretched extended run down MA 1A to Wonderland and then fight tunnel traffic to Haymarket because of the lack of a Blue Line extension tying those at their home terminal. The equipment supply is perpetually imbalanced by the extended running, capping frequencies across the North Shore at no-growth…with gradually worsening on-time performance as 1A gets more congested. The anemia hits hardest at the northern reaches when Salem has useful diverging routes but the supply chain is absolutely shot getting the buses there from Lynn. Getting the frequent train service implanted up to Salem/Beverly means you can potentially shear off Salem as an origin-destination hub in its own right for last-mile trips hosting its own breakaway equipment supply, be it under the T Yellow Line banner or some new North Shore transit entity. Chop via route reorganization the fragile tendrils of all those routes needing to run out of Lynn and grow a new home network for Salem, Beverly, Danvers, Peabody, etc. out of Salem hub with equipment rotations capable of delivering the transformative last-mile frequencies that they can’t today being shackled to Lynn. You’d have numerous new options to swarm Salem, Beverly Depot, Peabody Square with new diverging route options that had frequencies to matter. That’s another one to consider if the outflow of these Regional Rail connectivity efforts lands a big “RTA’s Rejuvenation” bill in front of the Legislature. At the very least I’d love it if TransitMatters placemarked that outflow a a more prominent agenda item for hashing out the early-Phase implementation on the North Shore.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.