A Strange View of Transit Priority

At last night’s Community Liaison Committee meeting on the West Don LRT project (aka Cherry Street streetcar), I heard a rather bizarre definition for “transit priority” that will be used to evaluate various design options:

“Transit Priority” means that transit will get at least as much green time as the through auto traffic at an intersection.

Hmmm.  Let’s compare this with what we have today.

On the Harbourfront line, the streetcar has to wait for its own green cycle which is much shorter than the green time for traffic, and is so short that it sometimes prevents more than one car from getting through on a cycle.  Clearly not a model for transit priority.

On St. Clair, the detectors don’t seem to be working everywhere, and there are left turn phases blocking the streetcars (and through traffic) even when there is nothing waiting to make the turn.  If this blockage occurs in only one direction, then one of the through road movements gets more green time than the streetcar.

On Spadina, the detectors actually work, and if there is traffic waiting in the queue only for one direction, the other one gets a green for the cars before the green for the streetcar.  If there are left turns both ways, the streetcar and other traffic get the same green time.

On a regular street in mixed traffic, everybody gets the same green time although left turns can block the movement of both through traffic and streetcars equally.

Nowhere in this list is there a model where the streetcar pre-empts the left-turning movements and is able to cross the intersection for the majority of the cycle.  Instead, the emerging standard appears to be that left turns pre-empt everything in their path.

Maybe we should call it “left turn priority” since these are the only moves that really benefit from this scheme.

“Transit priority” means “transit first”, not transit in the five seconds we grudgingly spare from everyone else.

27 thoughts on “A Strange View of Transit Priority

  1. Things like this that will make Transit City a total failure. I do agree with some lines, like Morningside, Jane, but some like Eglinton (as well as Don Mills south of Eglinton) are not practical for a streetcar (oh… right, sorry… LRT). It will not adequately serve Eglinton’s dual purpose (a regular local service and speedy cross-town travel option) as a streetcar, it just cannot be done if traffic lights and speed limits are shared and the same as cars’, and Eglinton is the most significant corridor of Toronto’s future.

    Lots of people have been able to point out some glaring elements of stupidity on the design of some of the existing transit priority ROWs. Things like putting the stop in front of the light… somebody needs to fired for incompetence, putting the station after the light is fundamental.

    As for left turners, make the lefties go last on a separate signal instead of the advance green.


  2. I thought transit priority was when the streetcar or bus interrupted the traffic light cycle to give conflicting traffic a red light for 5-10 seconds while it passes the intersection, and does not necessarily need as much green time as a car? When you read this, it sounds like it is just adding an intermediate transit cycle to the lights.


  3. It’s a classic case of how important definitions/goals can be. Meeting this “transit priority” goal sounds like a juicy technical challenge, but it might accomplish very little in improving transit.

    I’d define transit priority as “Under normal conditions, transit vehicles are not impeded by red lights.” With e.g. five minute headways that’s probably a lot less green time for transit than for autos; it’s the timing of those greens that matters.


  4. For the love of god, I hope this symptom will not apply to the new Transit City lines when completed. If this doesn’t happen, this would be a huge step backwards for quicker transit in private ROWs. I’m actually curious to know who I should vent my frustration too regarding transit signal priority. Steve, is there anyway I can be proactive here?


  5. I have a problem with the very definition provided. Transit priority should not be so much about how much green time a streetcar has per cycle as it should be about, a) which mode of transit gets a green after a red light (right now that tends to be left turning traffic) and b) the ability of streetcars to manipulate or modify traffic light cycles in order to expedite a green cycle for the streetcar.


  6. The days of light-and-sensor intersections are over. We need a system that sees the streetcar coming from a kilometre away, and is green when it gets there.


  7. How hard is it really to estimate the time a vehicle will take to get to a light and time the light such that it will be green by the time it gets there? Aren’t our lights already timed to do that for cars based only on when the previous light turned green?

    I’d really like to see how other cities handle transit priority for light rail routes. Because as it is I don’t really know what can be done. Is never waiting for a red light just a dream or can it actually be done?


  8. I just noticed on the Queensway, at the traffic light intersections, signs that say “STREETCARS 7 KM/H”! Why 7 when the automobiles are going 60+?
    Is this the same person who put them up the “BICYCLISTS DISMOUNT CROSSING ROAD” on the Eglinton West bike path, but which nobody does and ignores while riding?

    There should be a left turn signal at eye level right beside the left turn lane, shining right into the first driver’s face, like in Europe.


  9. That system would be GPS. It would also be very useful for keeping headways regular on 501 Queen.


  10. Well I just don’t understand why we don’t follow Calgary’s model, minus the railway barriers. There, when an LRV approaches a crossing, the barriers go down just before the train arrives, and go back up after it has passed. On Toronto streets, a similar method could be employed whereby all lights go red for an approching LRV, while the transit light goes green for a few seconds to let it pass through. THAT is signal priority.

    Granted, this will make the traffic people nervous, and they will claim that it would screw up the traffic flow of our streets. But if we don’t have true signal priority, Transit City will not provide service that is faster than the current buses plowing those routes, so what’s the point?


  11. Put all stations after the lights, and put a trip in the tracks shortly after the previous traffic light intersection that lets the intersection know a) there is a streetcar there and b) how fast it is going. The rest would be common sense and basic math.

    Steve: That is the basic idea, but the traffic folks claim that it would totally screw up traffic on the cross-streets due to the frequency of streetcar service.


  12. Steve said, “‘Transit priority’ means ‘transit first’,”

    I have to slightly disagree with that statement. I say “slightly” because there are times my definition is in line. I believe that ‘transit priority’ means ‘transit proceeds when transit needs to proceed’.

    If that means that an LRT is ready to depart at the start of a green phase for its parallel road, then that means ‘transit first’. However, after using the LRT in Minneapolis a few months ago (I’ll be back there in two weeks, so I’ll take some closer notes), it occurred to me that the traffic signals where the LRT operated downtown as well as on a road median south of the airport, the signals had a significant degree of intelligence built into them. Whether the LRT received clearance to proceed at the start of a green phase or near the end of a green phase was a function of what the LRT’s operation needed.

    There is no point in giving an LRT the green light just because it is there. If it has just arrived at a stop, it will need to take on and discharge passengers, so the green phase can begin for automobile traffic. If the LRT has been there for several minutes when it is time to change to a green phase, then it should be first.


  13. I still think the best option is crossing arms. Much like those used on the C-Train in Calgary. The LRT network in Toronto would be most successful it had comparable priority to the subway.

    I don’t know if it could work in an inner city environment. Calgary has not been as successful in the old city. The downtown region does not have traffic priority, while Sunnyside Station was very controversial. The Sunnyside Station works quite well today, but Toronto could face a uphill fight to build it right across the city.

    In Edmonton it seems to be working quite well in the inner city. Not sure what they did different (other than the tunnel in downtown). Maybe it is because the LRT is more familiar to Edmontians now, than it was to Calgarians during the Olympics.

    But to be fair Toronto has more similarities to Edmonton than it does to Calgary. Then again worse come to worse, crossing arms could work in Mississauga and Brampton.


  14. Aman Hayer writes about the benefit of “crossing arms” for intersections with LRT, or as I like to refer to it as “railway-style crossings”.

    This is practical in some situations but not others. One situation where it works quite well is when the LRT right of way is on one side of a parallel street. One of the best examples of this is in Minneapolis on Hiawatha Avenue. Calgary does use this type of crossing in a few places where the LRT runs in a median, but the median is fairly wide and the crossing street has room for vehicles to stop at the crossing in the median space. I have been documenting different systems from the point of view of what could be done in the GTA on my LRT Information Page (at http://www.lrt.daxack.ca)

    I can see the use of a one-side-of-the-road right of way being used in some of the suburban implementations of Transit City.


  15. I was on the St. Clair streetcar at around 3:30 pm yesterday, going from St. Clair to St. Clair W. stations. I don’t have much to say about the signal priority, because I wasn’t paying 100% attention to the signals, but what I can say is that the trip was smooth and FAST! I was very impressed by the speed of the service, noticeably quicker than the Spadina ‘LRT’ and any of the other on-road streetcar routes. 3:30 is not necessarily a busy time, but it seems to me they have done something right on St. Clair.


  16. I’ve had experience installing Wireless Opticom from 3M for emergency vehicle traffic signal pre-emption, and it has transit applications as well.

    Just outfit each desired intersection signal with a receiver and give the LRT vehicles transmitters.

    There are some settings that will cover each case:

    1. LRT arrives during green -> hold green until LRT passes through the intersection.

    2. LRT arrives during red -> switch early to green to give priority to the arriving LRT so it doesn’t have to slow down.

    Some municipalities currently use this for Fire Trucks.


  17. The whole LRT v motor vehicle issue is a major reason why I’ve been banging the drum to put LRT on existing rail ROWs where it is almost totally grade-seperated from street traffic.

    It seems that the MoveOntario plan will take advantage of these ROWs but under the GO banner. So whether it will serve 905 commuters mainly, as with existing GO services, or serve more as an urban transit system, integrated with subway and streetcar, with some stops between the 905 and downtown remains to be seen.

    Admittedly, I’m no engineer or transit expert but it just seems simpler to me not to lay new track on already congested streets if existing rail ROWs could be used.

    Steve: There are two very different types of travel. One is quite well-suited to existing railway corridors while the other requires local access by people on the streets where they actually live and work. This will become even more important as the suburbs increase in density with the Avenues plan. That’s why Transit City routes run on roads, not rights-of-way.


  18. “The traffic folks claim that it would totally screw up traffic on the cross-streets due to the frequency of streetcar service.”

    Am I the only person who thinks that we should stop listening to what the traffic people claim. I mean seriously, do they all live far out in the suburbs and drive cars, because there is no way in certainty that any of them have ever ridden the 510 and had to wait for 2 or 3 green cycles when streetcars get backed up.


  19. I recently made a few calls about the status of signal priority on Spadina. I understand Steve requested a report on this from TTC in 2003 and that the City had not responded.

    There is now some kind of joint working group looking at a city-wide policy on transit priority. I’ll follow up on this.

    It might be good to arrange a big sit-down interview with the City, TTC and Steve as well as UofT CivEng professor Baher Abdulhai, who has a few opinions about signals…

    Could be quite the debate.


    Steve: Yes, this would be extremely interesting. With luck, some priority will be given to organizing such a meeting. An important component will be to deal with the differences between downtown where streets tend to be 4-lanes wide most of the time and suburban intersections that have as many turn lanes as through lanes and a lot fewer pedestrians.

    It’s not a one size fits all situation.


  20. The Canadian government has a study completed in 2006 by Lea Consulting on transit signal priority algorithms.

    It’s a little technical…

    Steve: [Update added at 7:45 pm]

    I have reviewed this study and relative to our situation on major streetcar routes in Toronto, it has several shortcomings:

    The line used for simulating the effect of various schemes is a bus route (Brampton’s Main bus) operating on a 10-minute headway in the afternoon peak.
    The bus runs in mixed traffic in the curb lane, not in a centre reservation.
    Although it is not mentioned explicitly in the text, provision of a separate phase for left turns does not appear to be a major component, if any, of the simulated operation. Left turning traffic has less potential conflict with curb running buses than with centre lane streetcars.
    The cross streets are generally minor relative to the main street.
    The main road allowance is only 6 lanes wide including turn lanes. This affects the minimum green time needed to serve pedestrians crossing this street.
    The stops in the sample configurations are all nearside, although the modelled route includes some farside stops.

    The recommended scheme, which exists only as a model, involves a considerably more sophisticated approach to managing transit priority than we have in place. Indeed, the base case scheme (called level I-0 in the study) matches what we have in Toronto — detector loops in advance of and at an intersection to request priority at the next traffic signal. We do not have any of:

    Predictive operation of signals based on current traffic flows and expected dwell times at stops.
    Provision for schedule integration so that early or out-of-service vehicles are not given priority.
    Provision for cross-street route integration so that a decision on priority is based on conditions for all vehicles at an intersection, not only the first one that happens to arrive and request a priority sequence.
    Absolute pre-emption for emergency vehicles, or the ability of an operator to signal a readiness to proceed from a nearside stop.

    The study shows some improvement in speed and running time on the simulated route. More is achieved in the aggressive, intelligent system that adapts to changing conditions as proposed the study compared to the base case “dumb” model such as our operation in Toronto. It also shows less interference with green time for cross-street traffic probably because it makes better choices about exactly when the through street really needs transit priority.

    However, the study mentions, but does not address at all, the problems typical for most TTC routes where priority would be implemented whose frequency of service is at or below 2 times the normal traffic signal cycle at an intersection, let alone a situation where two such routes cross.

    This is an interesting exercise, but a bus running every 10 minutes isn’t going to make much of a dent in an auto-oriented riding habit, and one wonders whether spending more money on service to reduce wait times would be more productive than shaving a few minutes off with an extremely sophisticated traffic signal system.

    I hate to sound negative, but if we are going to study transit priority, let’s do so on a major transit route.


  21. Steve wrote: “However, the study mentions, but does not address at all, the problems typical for most TTC routes where priority would be implemented whose frequency of service is at or below 2 times the normal traffic signal cycle at an intersection, let alone a situation where two such routes cross.”

    2 cross-routes that are supposed to have priority happens on some routes more than others, but will become an increasingly common occurence to be sure.

    I don’t think the traffic folks really have a good argument when they say it will screw up traffic flow with such frequent service. Even half-a-minute is enough for letting through a half-decent amount of through-traffic and right-turners, and if they are changing every 30 seconds to a minute or so as per streetcars’ needs in both directions (and that would still apply even if only one of the two cross-streets has a streetcar running along it), traffic flow should be fine. Pedestrians?… maybe not the older ones.

    Such intersections with such frequent light-changes would likely require islands for pedestrians that cannot make the crossing in time, and they need to be spacious enough to accomdate people with mobility devices like walkers (as they are among the most likely to not make the full crossing in time). This kind of space management becomes a pain since there isn’t enough space for such, let’s face it. Without such islands, the alternative is a worthless transit priority system as a consequence of respecting the minimum time elderly pedestrians need to cross the street.

    Steve: The problem of long crossing times applies to streets like Spadina and many of the wide suburban streets where Transit City routes are planned. Half-way refuges for pedestrians need to be incorporated in the crossing design. Spadina posed special problems for this because the intersecting streetcar routes have curves that cut across the very location where such an island would be.

    Figuring out what happens when two signal-priority routes cross requires some programming. There are going to be many instances of both routes approaching the intersection at the same time. The first calculation should be does one route have both its directions waiting to pass vs. the other route’s one direction in waiting. Assuming it is one on one, simultaneous arrival, the next question would be “who’s on schedule?” This is a far more complicated question than it looks. The intersection would have to be keeping count of all streetcars passing through the intersection and cross-reference the schedule all the time, in Queen’s and College’s cases that’d be around the clock! Because if headways are about two minutes, a three-minute delay along the route will just through everything out the window for on-spot random checks.

    Keeping track like this I imagine would be complicated programming (and likely expensive to implement), but if it is reliably implemented, I imagine it would handle these situations extremely well. If two delayed cars arrive at the intersection simultaneously, whichever has a longer delay goes first, and if that’s identical too, then default to which route has a farther-away terminus (as per schedule, short-turns need not apply). In the event of simultaneous scheduled departures… let them crash and blame it on the author of the schedule.

    Steve: One question for the system modellers here is to find the point of diminishing returns. At what point does the increasing complexity and cost of a sophisticated signal control scheme outweigh the marginal improvement in transit movements.


  22. From Comment 18: Am I the only person who thinks that we should stop listening to what the traffic people claim. I mean seriously, do they all live far out in the suburbs and drive cars, because there is no way in certainty that any of them have ever ridden the 510 and had to wait for 2 or 3 green cycles when streetcars get backed up.

    Yes they do! Many City of Toronto employees live out here in Durham. This includes– TTC, Emergency workers, office workers– Senior Planners! – I know one of them. Only the politicians seem to live in the City. 🙂


  23. Perhaps we could trade our traffic planners for Ottawa’s. The roads people in Ottawa managed to find simple, effect ways to speed buses on their way like the left-turn-from-right-lane scheme and the turn lane queue jump. Both of these work by allowing the bus to start moving seconds before the cars, just long enough for the driver to cut the nose of the bus back into the proper lane before traffic could move. This was before the widely ignored bus priority rule came into effect.

    There was also a neat bit of traffic light timing that allowed buses coming off the Transitway onto the Ottawa River Parkway to sailing into that intersection with nary a check in speed. Great fun! Then again, Ottawa also has bicycle priority traffic lights on some of the suburban bike paths. They have embedded sensors in the bikepath far enough ahead of the intersection of road & bikepath that by the time you cycle up to the road, the lights for the path are green.

    The last thing we need is extremely expensive railway crossing gates (I once heard that a railway crossing can cost more than $250,000) where all we really need is an extra light aspect (the white rectangle) and some political will. Especially when transit priority should apply to all transit vehicles at every congested intersection.


  24. Karem – we already know Gary Webster’s interview from the Star that the TTC GM doesn’t live in 416. Personally I would like to see, at a minimum, all appointed agency Chiefs live in 416 as a condition of employment – in computing the term would be “eating your own dogfood”.

    Getting back to the matter at hand, I’m not sure we can avoid playing favourites with routes, especially downtown. That said the junctions where two trunk routes intersect account for a fraction of the total on a given route and if we can at least prioritise TC and existing trunk routes like St Clair LRT over non-trunk routes, and non-trunk routes over roads with no transit, this is better than the baseline with savings of both time, fuel and vehicles needed for a given headway.

    The worry I have about an “adaptive” system would be its robustness, so that if it encountered a system failure that it could “gracefully degrade” to at least being no worse than a dumb system rather than completely imploding and causing gridlock.


  25. This is a digression but the city could not legally require staff to live in the city. In Canada there is a constitutional guarantee of mobility rights (see para. 6 of the Charter of Rights and Freedoms). Even with the new powers the city has it cannot override the charter of rights.

    Rick Ducharme lived outside the 416 and took the subway and GO on a regular basis. I think he knew what was going on without living in the 416.

    The City’s entire traffic management system seems to be technologically challenged. There seems to be no desire to actually have any flow to road traffic, it’s almost as if the lights are on some sort of random program.


  26. The advantage of the Cherry Street LRT should surely be that there isn’t much of an existing neighbourhood compared to what is planned for the next few years. The usual arguments about traffic flow and damage to existing businesses during construction shouldn’t be as marked because the developments feeding the LRT are coming at more or less the same time. That’s why I think this line should particularly expedited so that Torontonians have an example of an LRT which operates in the best possible conditions.

    @Michael, Toronto restricts some ABC appointments to Toronto residents. s.6 refers principally to interprovincial mobility (e.g. Law Society of Ontario vs Skapinker). I’d love to get into that further with you but I don’t think Steve would love it.

    Steve: I am not sure if I’m up to moderating posts about the finer points of jurisprudence.


  27. Transit priority should include having a callable streetcar (LRT) phase both before and after left turn phases. For a “leading left”, if a streetcar was already waiting then a five second or so streetcar-only phase precedes. If the streetcar arrives after the left turn phase begins, it proceeds concurrently with the straight through traffic movements that follow the left turn phase.

    The success of this depends on other vehicles not fouling the track while waiting for their green phase.


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