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How is the State of Texas and/or City of San Antonio supposed to pay for this?
The same way they want to pay for the infrastructure that will allow them to vary the speed limit: with tax revenue. And yes, they need to stop the diversion of fuel tax revenue.
Because if there is a slow down, or worse a stop in traffic, if they can get the cars that haven't gotten to that point to slow down before they get there, is lessens the damage. Have you ever gotten to a spot on the road where everyone is slamming on their brakes and there's no clear reason why? Quite often one of the causes of that is someone did something dumb, someone had to slam on their brakes, then the person behind them does, then the person behind that person does and so on. An hour later you've still got people slowing down at that spot. What the VSL signs can help with, if the people actually follow them, is slowing traffic down before they get to that point, so that when they get to that spot, they don't have to slam on their brakes, maybe not slow down at all and that incident disappears altogether.
That would be nice if it works. But having ample capacity will give drivers the option to change lanes and go around, rather than slam on the brakes and remaining in the same lane as the person who just hard-braked.
That would be nice if it works. But having ample capacity will give drivers the option to change lanes and go around, rather than slam on the brakes and remaining in the same lane as the person who just hard-braked.
Well, unfortunately, that "ample capacity" is very expensive to build & maintain.
The same way they want to pay for the infrastructure that will allow them to vary the speed limit: with tax revenue. And yes, they need to stop the diversion of fuel tax revenue.
cost of building infrastructure that allows for variable speed <<<<<<<<<<<<<<<<<<< infrastructure needed to keep up with growing population.
Especially when this is all paid with 1991 dollars.
Loop 1604 is not at that point. There is room to lay additional pavement on either side of, and in between, the existing main lanes (of course, they'd want to toll them...). There is also the possibility of building an upper deck, although I'd argue that is not necessary at this point.
Loop 1604 was one of the test sites, but it wouldn't be necessarily be deployed there and wouldn't be the only site where it could be deployed. Roads like Loop 410 North and the freeways around downtown, which don't have room to expand, could have it deployed there.
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Originally Posted by Slowpoke_TX
And how does slowing traffic "make it more efficient?"
Some quotes from a Texas Transportation Institute document on variable speed limits (emphasis is mine):
Variable speed limit systems "monitor data coming from roadway sensors and automatically adjust speed limits when congestion thresholds are exceeded and stop-and-go traffic is imminent. The speed limit is lowered to obtain a consistent and homogenous traffic flow at a speed that is sustainable with the traffic volume. This will delay the onset of stop-and-go conditions and reduce the number of rear-end collisions at the back end of the queue."
"Congestion-Related Variable Speed Limits are used when traffic volumes are building and congestion is likely. When volumes and/or speed exceed a predetermined threshold, the operational strategy is deployed. The intent is to handle more traffic volume at a slower, but not stop-and-go, speed."
"Variable speed limits can help delay the onset of congestion. With more uniform speeds and decreased headways, traffic flows more smoothly and efficiently, which can improve trip travel time reliability."
"Facilities in Germany with variable speed limits had travel times reduced by 5 to 15 percent, the number of crashes decreased by 30 percent, and a five percent increase in the maximum volume handled by the road."
I also don't understand how decreasing the speed limit makes any sense. If traffic is flowing 55MPH in a 70MPH zone, there is no need to reduce the speed limit to 55 (or less), as traffic is physically unable to move at the posted speed limit.
That's a simplistic understanding of how it works. The signs show the maximum safe speed. So if there was an opening where traffic could speed up to 70 again, those signs are informing folks that it's not safe to do so because the traffic is slowing down again downstream.
Last edited by TexHwyMan; 06-14-2016 at 06:09 PM..
"Variable speed limits can help delay the onset of congestion. With more uniform speeds and decreased headways, traffic flows more smoothly and efficiently, which can improve trip travel time reliability."
"Facilities in Germany with variable speed limits had travel times reduced by 5 to 15 percent, the number of crashes decreased by 30 percent, and a five percent increase in the maximum volume handled by the road."
I still believe that having ample capacity would reduce or eliminate congestion, thus reducing or eliminating the need for congestion management strategies. Congestion management strategies treat the symptom, not the problem.
And comparing German traffic to South Texas traffic is apples-to-oranges, considering the differences in driver behavior between the two locales.
Quote:
Originally Posted by TexHwyMan
That's a simplistic understanding of how it works. The signs show the maximum safe speed. So if there was an opening where traffic could speed up to 70 again, those signs are informing folks that it's not safe to do so because the traffic is slowing down again downstream.
I think you responded to something other than what I posted. If traffic is only flowing 55 MPH along a stretch of road signed for 70MPH, then it does no good to reduce the speed limit along that stretch of road, because the slower flow of traffic renders the posted speed limit irrelevant. IOW, I was focusing on one area of congestion. If you're arguing that the speed limit should be reduced at the outflow of one congested area in order to reduce the onset of congestion at the inflow of another congested area DS of the first, then that would make sense.
I still believe that having ample capacity would reduce or eliminate congestion, thus reducing or eliminating the need for congestion management strategies. Congestion management strategies treat the symptom, not the problem.
The money isn't there to increase capacity, and even if it was it is an extremely lengthy process. Projects like these signs help and don't take nearly as much money or time to design, improve and implement.
Quote:
Originally Posted by Slowpoke_TX
I think you responded to something other than what I posted. If traffic is only flowing 55 MPH along a stretch of road signed for 70MPH, then it does no good to reduce the speed limit along that stretch of road, because the slower flow of traffic renders the posted speed limit irrelevant. IOW, I was focusing on one area of congestion. If you're arguing that the speed limit should be reduced at the outflow of one congested area in order to reduce the onset of congestion at the inflow of another congested area DS of the first, then that would make sense.
The process of traffic slowing down from speed often creates an even bigger mess, so keeping traffic from speeding up just to slow down again downstream actually helps traffic flow overall in many cases.
The money isn't there to increase capacity, and even if it was it is an extremely lengthy process. Projects like these signs help and don't take nearly as much money or time to design, improve and implement.
Obviously, the process needs to be streamlined. And funding is there, if the political will is there. After all, they've never said "the funding's not there" for projects like streetcars, toll lanes, etc.
Quote:
Originally Posted by prim8
The process of traffic slowing down from speed often creates an even bigger mess, so keeping traffic from speeding up just to slow down again downstream actually helps traffic flow overall in many cases.
I thought that's what he was referring to, and that makes sense, but his reply confused me because his reply involved a broader scope than my previous post.
Obviously, the process needs to be streamlined. And funding is there, if the political will is there. After all, they've never said "the funding's not there" for projects like streetcars, toll lanes, etc.
Uhh, tolls are the funding source for toll lanes. The reason toll lanes are proposed, is due to a shortage of funds available to build needed additional lanes. But locally, at least, there is heavy opposition to paying tolls to drive on a road, so the bottom line is those lanes didn't get built.
The streetcar funding was to have come from multiple sources, including City money, the State's Texas Mobility Fund, the Advanced Transportation District, and some Federal funding. But that project has been dropped, for the foreseeable future. At least some of that money would have diverted from planned future road improvements.
I still believe that having ample capacity would reduce or eliminate congestion, thus reducing or eliminating the need for congestion management strategies. Congestion management strategies treat the symptom, not the problem.
Ample capacity helps until that capacity is either outstripped by demand or reduced due to other factors (i.e. incidents.) At some point, you just can't build your way out of congestion.
Quote:
Originally Posted by Slowpoke_TX
And comparing German traffic to South Texas traffic is apples-to-oranges, considering the differences in driver behavior between the two locales.
Then tell that to the Texas Transportation Institute since that was in their publication, and I know the Federal Highway Administration also quotes various European studies in their own literature on VSLs. The reason is that Europeans have much more experience with it. Over time, the data from US implementations will build, and I'm sure it will show similar results. The pilot in Texas already did to some degree.
While driver behavior is certainly different, the basic laws of physics and traffic flow are universal. That's why US transportation engineers frequently visit Europe to see what they're doing and vice-versa.
Quote:
Originally Posted by Slowpoke_TX
I think you responded to something other than what I posted. If traffic is only flowing 55 MPH along a stretch of road signed for 70MPH, then it does no good to reduce the speed limit along that stretch of road, because the slower flow of traffic renders the posted speed limit irrelevant. IOW, I was focusing on one area of congestion. If you're arguing that the speed limit should be reduced at the outflow of one congested area in order to reduce the onset of congestion at the inflow of another congested area DS of the first, then that would make sense.
Quote:
Originally Posted by prim8
The process of traffic slowing down from speed often creates an even bigger mess, so keeping traffic from speeding up just to slow down again downstream actually helps traffic flow overall in many cases.
Quote:
Originally Posted by Slowpoke_TX
I thought that's what he was referring to, and that makes sense, but his reply confused me because his reply involved a broader scope than my previous post.
Thanks prim8 for helping to clarify for me; that's exactly what I thought I was saying.
Quote:
Originally Posted by prim8
The money isn't there to increase capacity, and even if it was it is an extremely lengthy process. Projects like these signs help and don't take nearly as much money or time to design, improve and implement.
Quote:
Originally Posted by Slowpoke_TX
Obviously, the process needs to be streamlined. And funding is there, if the political will is there. After all, they've never said "the funding's not there" for projects like streetcars, toll lanes, etc.
No, the funding is not there, and political will won't be there because nobody wants their taxes increased. As I posted over in the 1604 thread, there are tens of billions of dollars of projects just in San Antonio over the next 25 years that will not be funded unless funding is greatly expanded. Then, there's the environmental approval process, which for a freeway expansion project takes years to complete. There is virtually no chance that will ever be streamlined. In fact, in San Antonio's case, it's about to get worse because we're likely to exceed federal air pollution thresholds in the next few years.
Toll roads are self-funding, and transit projects generally come from a separate pot of money; many transit projects don't get funded either.
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