Which is more effective for better transit? Signal Priority or Dedicated ROW?

[dunkalunk]

Ideally, you'd have a combination of both (like what they should have on Spadina), but if you only could pick one, which one would you choose for congested downtown bus and streetcar routes?

 

[EnviroTO]

Conflicts with other traffic is what slows transit the most. On a route with heavy automobile congestion signal priority will do nothing. Signal priority will not reduce accidents with the transit vehicles nor deal with the myriad of vehicles turning at every side street and driveway.

 

[dunkalunk]

Signal priority can be effective if it includes advanced greens and turn restrictions, and in places where it would not be practical to narrow the existing road (Like Roncesvalles) it could be quite effective.

 

[gweed123]

This is a rather misleading question. Is this total effectiveness, or minutes saved per dollar spent? Dedicated ROW is much more effective than signal priority, but the two are not even in the same ballpark in terms of costs.

Also, it depends on ridership volumes. You can have all the signal priority you want, but if you have buses carrying 7000 pphpd, that signal priority isn't going to do very much. But if you have a bus route carrying a couple thousand, then you may see some solid benefits.

 

[reaperexpress]

I have no idea how anyone (let alone anyone on this forum) can conclusively answer this question. There is an immense range in the design of both, and they aren't even mutually exclusive.

Maybe if we're talking about the TTC in particular we can compare how they implement the two concepts (quite poorly in both cases). But then it would be a question to be answered with statistical measurements (speed, cost, impact, etc), not a discussion on a forum.

 

[Electrify]

Before I vote, how "dedicated" are we talking about? are we talking separated traffic lanes, or full grade separation?

It also depends on the area implemented. If having to choose mutually between one or the other, transit lanes can work exceptionally well where the lights are spread out, but signal priority might be better in areas where the density of traffic lights is higher.

 

[BMO]

I think progression goes dedicated ROW-> Signal Priority as frequency of line increases

 

[gweed123]

I think progression goes dedicated ROW-> Signal Priority as frequency of line increases

It depends on:
1) Ridership
2) Vehicle type
3) Frequency of stops
4) Frequency of intersections that have lights

 

[BMO]

It depends on:
1) Ridership
2) Vehicle type
3) Frequency of stops
4) Frequency of intersections that have lights

On a congested Road, a dedicated ROW will improve the commute drastically regardless of light spacing/timing.

When capacity of the line is reached, this can be extended with signal priority to improve the efficiency of the line and get more trains through in a smaller span of time.

Of course you are correct in all those factors that are depended on to tailor the service, but I was making a general remark on how I think t should be done in a sensible and cost effective manner. IMO

 

[gweed123]

On a congested Road, a dedicated ROW will improve the commute drastically regardless of light spacing/timing.

When capacity of the line is reached, this can be extended with signal priority to improve the efficiency of the line and get more trains through in a smaller span of time.

Of course you are correct in all those factors that are depended on to tailor the service, but I was making a general remark on how I think t should be done in a sensible and cost effective manner. IMO

If it's on a suburban arterial, signal priority matters more (although I would couple that with queue jump lanes). On a congested urban arterial, dedicated right-of-ways matter more.

 

[reaperexpress]

If it's on a suburban arterial, signal priority matters more (although I would couple that with queue jump lanes). On a congested urban arterial, dedicated right-of-ways matter more.

I'd say it's the exact opposite. Urban roads tend to be slowed primarily by the frequent traffic lights. If transit could get itself a green wave, it would be able to travel quite effectively.

A suburban arterial, on the other hand, is more prone to complete gridlock: it doesn't matter what the signals read when the transit vehicles approach the intersection, it will take more than a signal phase to get to the front of the queue anyway. Here, a dedicated lane would help more, allowing transit to jump the queue and proceed on the next available green.

As well, signal priority becomes less and less effective as the frequency of intersections increases, because the signals can't reasonably predict when the vehicle will arrive at the intersection when there are many other traffic lights between it and the lights.

 

[EnviroTO]

I'd say it's the exact opposite. Urban roads tend to be slowed primarily by the frequent traffic lights. If transit could get itself a green wave, it would be able to travel quite effectively.

True if there isn't congestion preventing it from flowing with the lights.

A suburban arterial, on the other hand, is more prone to complete gridlock: it doesn't matter what the signals read when the transit vehicles approach the intersection, it will take more than a signal phase to get to the front of the queue anyway. Here, a dedicated lane would help more, allowing transit to jump the queue and proceed on the next available green.

I don't think either is prone to gridlock more than the other. Yes, in a suburban environment more traffic will be stopped at the same light because there are less of them and they may not get through the first cycle of the light... but there are much less lights so getting through one light in 3 cycles could be the same as getting through 3 lights in 1 cycle in terms of distance over time. But you are correct, in this case a dedicated lane provides greater value due to the level of congestion at the light.

As well, signal priority becomes less and less effective as the frequency of intersections increases, because the signals can't reasonably predict when the vehicle will arrive at the intersection when there are many other traffic lights between it and the lights.

No. It is easy to handle multiple lights when there is low congestion. The trigger is placed at the point the vehicle will be where there is significant enough time to cycle the light to green by the time the vehicle arrives and when there is no congestion and no stops between the vehicle and the light in question things are very predictable. Transit stops with passengers taking varying amounts of time to load and congestion create the unpredictability.

 

[W. K. Lis]

Suburban arterial roads tend to have less crossroads of them than downtown arterial roads. Most of them are with traffic signals. However, if an incident happens that blocks the roadway, there are no alternate detour roadways available in the immediate area. If there is a crossroad, the suburban roads around that crossroad curve this way and that way and have cul-de-sacs where the motorists get lost trying to get around the blockage. What happens is that the blockage ends up being greatly than it would be in downtown.

 

[gweed123]

I'd say it's the exact opposite. Urban roads tend to be slowed primarily by the frequent traffic lights. If transit could get itself a green wave, it would be able to travel quite effectively.

A suburban arterial, on the other hand, is more prone to complete gridlock: it doesn't matter what the signals read when the transit vehicles approach the intersection, it will take more than a signal phase to get to the front of the queue anyway. Here, a dedicated lane would help more, allowing transit to jump the queue and proceed on the next available green.

As well, signal priority becomes less and less effective as the frequency of intersections increases, because the signals can't reasonably predict when the vehicle will arrive at the intersection when there are many other traffic lights between it and the lights.

I would tend to debate that. Urban arterials are much more prone to crawling along than suburban arterials are. Queen Street crawls along at pretty much all daylight hours. Outside of rush hour, a street like Bayview flows pretty well. The delay on suburban arterials happens when an arterial meets another arterial, and they both require long complicated light cycles. If buses can get queue jump and signal priority at these locations, it would do wonders for their efficiency.

I guess what I'm saying is where is the gridlock located. If it's just at intersections, signal priority and queue jump lanes are better. If it's along the entire stretch of roadway, dedicated lanes are better.

 

[BMO]

I would tend to debate that. Urban arterials are much more prone to crawling along than suburban arterials are. Queen Street crawls along at pretty much all daylight hours. Outside of rush hour, a street like Bayview flows pretty well. The delay on suburban arterials happens when an arterial meets another arterial, and they both require long complicated light cycles. If buses can get queue jump and signal priority at these locations, it would do wonders for their efficiency.

I guess what I'm saying is where is the gridlock located. If it's just at intersections, signal priority and queue jump lanes are better. If it's along the entire stretch of roadway, dedicated lanes are better.

I agree with Gweed on this. Suburban arterials are more capable of providing better service with cue jump lanes and signal priority. In a congested downtown street even if cue jump lanes and signal priority is given the transit vehicles would end up being caught up in the congestion unable to get to those cue jump lanes, etc. Not to mention with a transit vehicle cue jumping and stopping in 1 block, has a much larger affect on traffic than in a suburban arterial.