#transit explained

[sfmuniverse]

It’s a dreadful feeling — you’re waiting at a bus stop, and when your bus finally shows up, it doesn’t stop to pick you up. Just when you expected the wait to be over, you’ve got to start it all over again.

Muni works hard to eliminate incidents known as “pass-ups,” which every transit system grapples with. However, many of these cases may have reasons behind them that may not be evident to waiting customers who are left behind. While Muni continues to tackle the issue whenever possible, we wrote this post to help shed some light and build more understanding.

It sucks to get passed up by a bus, but it’s not probably not because the driver is a jerk. The SFMTA asks that we file a complaint via 311 when they do happen so it can be tracked down in a post explaining some of the reasons why they happens.

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Transit Explained: The Downside of Dedicated Bus Lanes

Recently, the SFMTA released the final version of the Mission Street Muni improvement plan, without a northbound only one deidcated lane in the southbound direction. Earlier drafts had included lanes in both directions and 2/3 of survey respondants supported a Northbound transit lane as well. As the SFMTA explains it though, a dedicated lane in this case would end up doing more harm than good.

At intersections, right turning traffic would be mix with it, meaning the bus would not have it’s own lane where it matters most. Right turning traffic is delayed more than traffic going through.

It's pretty easy to see on a map how traffic turning and busses moving forward would get jammed up, while the center lane would be comparitively free for forward moving car traffic to bypass Muni.

The SFMTA does intend to add a limited amount of transit lane pockets at specific intersections which currently cause problems.

Transit lanes are only needed where there are queues or congestion blocking a bus’ path. Therefore it is important for a bus to have its own lane at intersections, and a transit-only lane is less important to have midblock.

Most importantly, transit lanes are only proposed in locations where they would have an effect, following a detailed analysis of every intersection.

At 16th & Mission is one of the special cases, with a short, dedicated lane just before the intersection. That will allow Muni busses bypass car traffic, which will be forced to make a right turn and clear the way for busses pulling up to the North-East BART plaza.

Periodically nudging motorits onto neighboring side streets with forced right turns has also demonstrated on Market Street (where cars are forced to turn at Tenth and Sixth) to distribute traffic more evenly before it reaches frequent pinch-points downtown and near freeway onramps.

Got a question about Muni or how transit works? Ask Muniverse, we might have an answer.

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Hey @sfmuniverse, why is the Duboce tunnel right side (entering) lower than the left (exiting)?

Between Church and Van Ness, the inbound and outbound tunnels separate vertically so the tracks are a fully story apart. Inbound trains enter the tunnel a sooner and steeper so they can pass under the outbound tracks without creating any conflicts.

The configuration is called a “flying junction” and works pretty much the same way freeway interchanges work, but you can’t really tell there's an underpass when it's inside a subway tunnel. Look down the tunnels at Church Station towards downtown and you’ll be able to see the tracks separate as soon as they get past the station.

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I was on the 22 (Fillmore), and saw two black boxes (about the size of AppleTV "pucks") facing each other, installed at all doors. Two red lights on the sides. Any idea what they are? MUNI counting people?

You guessed correctly, the devices are sensors which detect people crossing between. In 2006, Muni installed the first automatic passenger counterson about 10% of the bus fleet and started shuffling them around to collect ridership data for every bus lines. The data helped shape what's become the Muni Forward project.

The busses installed with sensors have a sticker in the upper right of the front window labeled “APC” to make it obvious to Muni staff which busses are which. We noticed the counters on one of the latest-generation of busses too and suspect it's a new design.

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On streets with overhead wires, I see these yellow markings: circles, something that kind of looks like a magnifying glass, and other symbols. I'm guessing they have something to do with switches in the overheard wires, but I'd love to know exactly how to read them. I'd also like to know the meanings of the various red/white lighted signals used by the streetcars and light rail.

You guessed right, those yellow circles painted on the street do mark the switches in the overhead trolleybus wire. They signal to the diver when their pole is going to cross another wire or comes to a switch. They're placed well ahead of the switch itself, where the front of the bus will be when the poles finally get there. For that reason they usually come in pairs (of pairs) for the shorter and the longer busses.We had some of it explained a few years ago, and as we remember it, a simple yellow cicle alerts the driver where the poles will cross another line, an alert to the driver.

Circles with a line sticking out show when the bus will cross will hit a switch. You can think of the line as where the poles should be when the driver reaches the switch. Sometimes that can be around the corner and the markings on 18th Street shown here are for switches around the corner along Castro Street.Because the circles mark where the busses will be, and not where the switches themselves are, two different switches might land busses at the same spot. So circles might have two lines sticking off in different directions.

We've also seen another version of the circle with a line passing through it, but we don't know what they mean. (If someone in the know or works for Muni could fill us in, we'd love to learn more)Besides crosswalks near schools and dividing streets in half, yellow is used for other transit markings and we found examples along the Church Street transit lanes where the track switches are marked in yellow on the red transit lanes with white stencilled "Muni/bus/taxi only" telling motorist to get out.

As for the signals white is used for transit signal lights – including the some of the stop signals – to avoid confusing motorists looking out for the red, yellow, and green lights. Light-rail and streetcar signals and signs are governed by a very legnthy document called the Manual on Uniform Traffic Control Devices (MUTCD), which is the Federal Highway Administation's rules and regulations.Trolleybus markings are someting specific to San Francisco so they aren't layed out in the MUTCD, but the traffic signals are standardized and this chart comes directly from the document.

Muni uses two-signal lights without a flashing triangle. A few other's Muni uses include white and red "T" signals, which we suspect that's to make it clear these are for the trolleys and not motorists. There's as a red X signal light that's the streetcar version of a stop sign.Having separate transit and traffic signals also means trains or cars can be given a head start at shared intersections. An example is at 18th & Church where J trains heading downtown are given a go signal, and only when there's a train present, before cars are given the green.

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Transit Explained: Signal Priority

Ideally the only time a bus, streetcar, or train would ever stop is for boarding and every traffic light in between would be green. Well, ideally there would be dedicated transit lanes or a completely grade-separated subway, but since that’s only an option for a few cases there’s transit signal priority.

Transit signal priority (TSP) works by mounting transponders on transit vehicles which relay their location to traffic signals as they approach.

The computer managing the traffic signal uses the location and speed to adjust the timing by a few seconds to hold the light green so a bus can get through. Timing won’t be cut so short pedestrians aren’t going to be stranded mid-block and there won’t be a green so short only one car gets through. This isn’t going to work every time, but they work enough of the time the savings add up.

Here in San Franicsco the SFMTA has installed more than 250 citywide and seen 4-5 minute (10%) savings on the 14-Mission.

When the stop is located on the far side of the intersection on the far side of the intersection, holding the light lets the bus get through the intersection, board, and move on by the time the light has turned green again for car traffic.

Illustration: SFMTA / Transit Effectiveness Project

Got a question about Muni or how transit works? Ask Muniverse, we might have an answer.

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Transit Explained: Far Side Boarding

Busses stop at green lights, which is annoying for everyone involved. If there isn’t enough room for a bus to pull over it blocks traffic, if there is room to pull over then the bus blocks up traffic pulling in and out of the stop. In cases where there’s a lot of turning traffic the bus stop might be taking up what would be a good turn lane. Or drivers who use it as a turn lane prevent busses from pulling over and the circle of traffic continues...

Moving the bus stop to the far side of the intersection – after the signal light or stop sign – means busses are going on the green light as well, with the length of the intersection giving them room to slide over to the side and out of way for through-moving traffic. Pulling back into the traffic lane is easier because a red light or stop sign just behind the bus provides a window between cars.

It seems pretty obvious and simple now, but like of other innovations, it took a lot of time and work to get to a simple solution.

Far side boarding is not always the right solution and there are a lot of reasons to locate a stop before an intersection, such as a transfer point or a major destination where passengers would all just be crossing the street anyway. The change up in thinking is to look at far side boarding as the default, unless you come up against one of those cases which justify making busses stop a green light.

Here in San Francisco, far side boarding was a adopted as the default standard last year and is being implimented as part of the Muni Forward program starting with designated priority corridors. In a lot of cases it isn't as simple as picking up the shelter and moving it across the street because there's wiring and signal changes involved.

Illustration: SFMTA / Transit Effectiveness Project

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Transit Explained: Red Lanes

A few years ago the SFMTA installed San Francisco's first transit-only red lanes along three blocks of Church Street as a pilot project. Transit-only lanes painted in various colors have proven their worth around the world, but the City first needed test and measure their performance before and after. That gave the City a way to make sure they worked, even at the six-way intersection at Market & Church & 14th, and make any tweaks before committing to them further.

The result was a 20% improvement in reliability and a 5% drop in travel times. With that, red lanes were approved for use citywide as part of the Transit Effectiveness Project, which is now being implimented under the Muni Forward name.

The project built up a toolkit of repeatable design patterns that can be applied in different situations depending on the issues. These design patterns are the building blocks of the Muni service overhaul getting underway and for the folk who don’t make it a habit of reading obscure planning documents we’re a starting a series of "Transit Explained" posts running starting here with the red lanes.

A transit-only lane is a travel lane that is dedicated for the exclusive use of transit vehicles. Transit-only lanes are typically identified with signs and pavement markings. Transit-only lanes can reduce transit travel times by allowing transit vehicles to bypass traffic congestion and avoid conflicts with other vehicles in mixed travel lanes.

Non-transit vehicles are generally permitted to enter transit-only lanes to access curbside parking or to complete a turn, unless specifically prohibited. Emergency vehicles may use transit-only lanes at all times, and often taxis may also use these lanes. Transit-only lanes can be created by removing an existing travel lane or by removing a parking lane.

Source: SFMTA / Transit Effectiveness Project

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