Feds give MARTA $12.6 Million for Rapid Transit Line

[cqholt]

Originally Posted by samiwas1

I agree with Fourthwarden. () While these may be "quick and affordable", putting them in an area leaving a single traffic lane means that the entire road stops with the bus at every stop. That may be okay for a small back road, but hardly acceptable for an arterial road.

I rather like the image that Fourthwarden shared, but it would need two lanes in each direction. But with four 10' travel lanes (preferably 11'), two 9' parking lanes, and two 5' bike lanes (at the very minimum), you need about 90' of ROW once you include sidewalks and whatnot. I'd prefer a design which allows a bus pull off in the same "lane" as parking is the rest of the route. Or, eliminate the street parking for deck parking.

Get rid of on-street parking and there is room for 2 lanes, dedicated bus lane, and protected bike lane. Midtown Alliance has the ability to work with underused parking garage owners to implement shared parking.

[cqholt]

Could this idea work in Atlanta, where many of our arterial roads are 2 lane?

Traffic signals that give buses priority at the intersection aren’t uncommon on arteries with dedicated bus lanes. Pre-signals, on the other hand, are a very rare bird of traffic planning: These traffic lights are placed mid-block—“upstream” from regular signalized intersections, as the engineers like to say—and actively change the flow of traffic before vehicles hit the intersection at all. This helps avoid conflict and delays amid crosscurrents.
To pull it off, both lanes get a pre-signal facing both directions of traffic. The pre-signal on the lane facing the opposite direction of the moving bus stops the flow of cars, so that a segment of the lane becomes clear for a bus to merge into it. Meanwhile, the pre-signal on the lane in the same direction also pauses its flow of cars, allowing the bus to merge back onto its original lane with the stopped cars behind it. This all happens before the main signal, avoiding conflict with cars in the intersection. “You get a de facto bus lane by utilizing the opposite direction lane to jump the queue of cars,” Gayah said in an interview.

https://www.citylab.com/transportati...a-lane/561509/

[Need4Camaro]

Originally Posted by cqholt

Could this idea work in Atlanta, where many of our arterial roads are 2 lane?

https://www.citylab.com/transportati...a-lane/561509/

It's difficult to say, I'd say probably in areas where intersections are a bit more spread apart it would definitely help busses. In areas where intersections are closer together it might not turn out so well though due to two factors:

#1 increasing the amount of signals within a relatively short vicinity is never a good idea and one of the leading causes of congestion

#2 Even if the bus did jump the queue of cars (legally in this circumstance), if there was a busy intersection ahead that the bus does not get priority over then he will still end up waiting behind the traffic waiting at that intersection and on most 2 lane roads, intersections with larger streets, the larger road typically has the longer priority green light.. Or basically, the only reason a bus would need to jump ahead of cars is.. if the traffic was not moving, but likely if it isn't moving its largely due to another intersection, so while he may jump the pre signal of maybe 3 - 5 cars, he still has to wait behind another 10 more to clear the cross street intersection (or worse, the dumb drivers stop in the intersection of the pre-signal preventing the bus to come back to the right side of the road, blocking on-coming traffic.)

This idea would work better if in conjunction however that after clearing the pre-intersection that he would be within minimum distance necessary to trigger a priority / mandatory green light at the intersection thus keeping traffic flowing enough for the bus to clear the intersection after the pre-signal keeping traffic on the 1 lane road moving as much as possible (which is required to keep the bus moving to get to the next pre-intersection.)

In a perfect world, another alternative is if they made turn on red arrow (both left and right) at the cross street, the actual intersection could also be used as a pre-intersection assuming noone made a turn onto the oncoming lane right into the bus thats driving down it to bypass the intersection

[cqholt]

Originally Posted by Need4Camaro

It's difficult to say, I'd say probably in areas where intersections are a bit more spread apart it would definitely help busses. In areas where intersections are closer together it might not turn out so well though due to two factors:

#1 increasing the amount of signals within a relatively short vicinity is never a good idea and one of the leading causes of congestion

#2 Even if the bus did jump the queue of cars (legally in this circumstance), if there was a busy intersection ahead that the bus does not get priority over then he will still end up waiting behind the traffic waiting at that intersection and on most 2 lane roads, intersections with larger streets, the larger road typically has the longer priority green light.. Or basically, the only reason a bus would need to jump ahead of cars is.. if the traffic was not moving, but likely if it isn't moving its largely due to another intersection, so while he may jump the pre signal of maybe 3 - 5 cars, he still has to wait behind another 10 more to clear the cross street intersection (or worse, the dumb drivers stop in the intersection of the pre-signal preventing the bus to come back to the right side of the road, blocking on-coming traffic.)

This idea would work better if in conjunction however that after clearing the pre-intersection that he would be within minimum distance necessary to trigger a priority / mandatory green light at the intersection thus keeping traffic flowing enough for the bus to clear the intersection within a short vicinity...

The leading cause of congestion is too many cars for the lane capacity.
Did you watch the video in the article? The intersection is cleared of cars before bus signal priority.

[Need4Camaro]

Originally Posted by cqholt

The leading cause of congestion is too many cars for the lane capacity.
Did you watch the video in the article? The intersection is cleared of cars before bus signal priority.

I saw it, its a interesting concept.

lane capacity is definitely an issue but multiple intersections in one area generally makes it worse.. but that aside my main thing isn't the pre-intersection.. but what happens after the pre-intersection.. you see likely, after the bus clears the pre-intersection, there are still going to be a queue of vehicles waiting at the next intersection for the cross street which the bus will still have to sit behind, and also.. if the vehicles crossing the pre-intersection do not treat it properly and block up the intersection (extremely common in the metro) then the bus will be stuck in the oncoming lane and block oncoming traffic.

I think what would help is, after clearing (or atleast mostly clearing) the pre-intersection, the bus triggers a priority green for the next cross street even if he is a decent bit of distance away from it, thus clearing the roadway of traffic, making it possible for the bus to continue moving after clearing the pre-intersection. As it would do the bus little good to jump ahead of a few cars and still wait in line for the next traffic signal.

I understand the concept, the idea is to keep transit traffic moving as much as possible but in practice it may not be as easy as it looks here.

Edit: Watching it again, in short - as long as the pre-signal is cordinated with the traffic light at the intersection preventing oncoming traffic from crossing the INTERSECTION and not just the pre-signal and the pre-signal stops traffic going the busses direction before they GET to the intersection (meaning no queue waiting for the cross street at the intersection) ...it should work.

It would work best something like this...

====================================
Scenario: All signals on the street the bus is traveling on are currently green.
1. Bus approaches pre-signal.. atleast within 5 car lengths.
2. The Pre Signal light changes red - a few more cars get through the pre-intersection before the cycle is complete
3. The Bus gets the first bus right of way signal to cross onto oncoming lanes -- THE INTERSECTION TRAFFIC SIGNAL REMAINS GREEN to allow remaining traffic to clear the intersection as to avoid impeding the buses path.
4. The Bus clears the pre-intersection -- At the cross street - for CROSS TRAFFIC - a No right turn on red signal illuminates to traffic awaiting at the cross street for BOTH directions. The traffic light at the Intersection remains green while the bus signal also illuminates allowing the bus to clear the intersection.
5. Bus clears the intersection, the pre-intersection signal remains red as to not allow traffic to queue between the pre intersection and the main intersection. The main intersection signal turns red to complete its phase, and the no right turn on red signals on the cross street deactivate.

----------------------
Scenario: The cross street has right of way.
1. The traffic light at the intersection AND the pre-intersection that the bus is traveling down remain red - the pre intersection signal will not allow traffic to queue at the intersection
2. The bus approaches the pre-intersection. At the cross street, for cross traffic - the traffic light changes red and no turn on red signs illuminate as to prevent traffic on the cross street from turning into or against the busses path. The bus signal at the pre intersection illuminates after all turning oncoming traffic has cleared the pre-intersection allowing the bus to cross into oncoming lanes.
3. The bus crosses the pre intersection and merges back into his lane -- the BUS ILLUMINATOR light at the intersection for the cross street illuminates only, allowing the bus to cross the cross street, the signal at the cross street however remains Red.
4. After the bus clears the intersection, the pre-intersection light changes green, and the cross street intersection light completes a phase, changing green for the traffic approaching from the pre intersection.

In all cases though, the signalization of such a project would not be cheap. The average 8 signal traffic light costs in the ball park of $300,000 -- add all the additional phases and programming and additional traffic lights, surveys, ect... it will go up...exponentially.

[samiwas1]

Originally Posted by cqholt

Could this idea work in Atlanta, where many of our arterial roads are 2 lane?

https://www.citylab.com/transportati...a-lane/561509/

That might work on a road which has no other entry points within that span. Many of these two-lane arterials though have houses or businesses lining them. Outside of that, the idea still looks patently ridiculous.