There are always complaints to the Public Works Department about traffic signals in Casa Grande, especially at busy intersections.
As Traffic Engineer Duane Eitel told the City Council during a recent study session, two of those intersections are Florence Boulevard/Trekell Road and Florence Boulevard/Arizola Road. The main complaint is that more time is needed for left turn arrows.
This year’s capital improvements plan calls for designing improvements at both, he said.
Arizola Road will require additional work, but Trekell/Florence could be just a matter of restriping lanes.
Eitel’s presentation covered only Trekell/Florence. He made clear that, at this time, it is only a concept. The city will issue a contract request for a professional traffic flow designer to do the final plan for that intersection and for Arizola/Florence.
“The predominant traffic flow at Trekell and Florence is going southbound, either turning right or they’re turning left,” Eitel said. “There’s more right and left turns than there are through traffic. So we thought, ‘Well, maybe could do away with one of those through lanes, make that a left turn lane and fit everything in there and have dual lefts – one lane southbound right, one lane northbound.’ Up by Cal Ranch intersection we would taper back into the four lanes, with the two-way left turn lanes.”
He added, “Traffic capacity-wise, we don’t need two lanes going through south of Trekell.”
That left the question of how to match up Trekell south of Florence, Eitel continued, “because you want the through lane to match –not necessarily go into two through lanes. Well, with that thought we revised what is called a ‘road diet,’ where you take a straight four-lane with no left turn lanes, no right turns lane and change it into one lane southbound and one lane northbound and a left turn lane in the middle and then we would put bike lanes on the outside edge.”
That would extend south on Trekell to about the elementary school, Eitel said.
“Now, what this does — it may sound odd — is the capacity actually goes up in an area like this where there’s a lot of left turns versus a straight four-lane,” he continued. “What happens in a straight four-lane if you’re driving in the through lane going south, somebody in front of you decides they want to turn left, you have to slow down and, quite often, somebody maybe makes the decision, well, I’ll just zip over to the right turn lane and go around them. Maybe somebody’s already there; they get over to the right turn lane and somebody decides to turn right and have to slow down there, (then) they zip back over to the left.”
That can often lead to accidents.
“There’s been a lot of research on this, that a three-lane design, where there are a lot of left turns, there are somewhere between 20 to 40 percent less crashes than a straight four. And the capacity goes up. The capacity of a three-lane design can be anywhere from 10,000 to 20,000 cars a day, and on Trekell Road south of Florence we have 4,800 cars a day,” Eitel said.
“In this case, it would be more bicycle and pedestrian friendly, because we would have the bike lane on the outside edge, and instead of having to across four lanes now, you only have to cross three as you’re walking.
How it would work
“North of C-A-L Ranch is where we taper out of the existing four-lane, left turn lanes, still keeping a left turn at C-A-L Ranch driveway and then we start dropping the lanes right after that, so from there we go into the dual lefts, one lane southbound, one lane northbound,” Eitel said.“The traffic north of Florence is higher than the traffic south of Florence. The traffic continually builds as you’re up to Cottonwood.”
Mayor Bob Jackson pointed out that under the present configuration northbound drivers try to make left turns into Pinal County Federal Credit Union.
“Is that going to be a movement that you no longer allow?” he asked.
That needs more study, Eitel responded, adding, “The two movements I wish we didn’t have there are both that one and the one going into C-A-L Ranch. They both cause a lot of issues there.”
Jackson said that several years ago, McMurray Boulevard was changed from a straight four-lane to three lanes – one in each direction and a turning lane in the center.
“I think the thing that we didn’t anticipate very well was the right turn volume,” he continued. “And I’m guessing there’s a fair amount of traffic southbound at that intersection (Trekell-Florence) and with this configuration now, everybody’s going to have to stop. The first guy in line wants to go straight; (the) next five people want to turn right, so you’re going to stop that whole queue of cars. Am I understanding that correctly?”
That will happen, Eitel said.
Jackson continued, “The flip side of that is, first guy in line wants to turn right and there’s a pedestrian in there, so you have to wait for that pedestrian to clear. I know you can’t solve every problem, but have we thought about trying to see if we can get some right of way from the bank for a right turn lane?”
Eitel responded, “We actually have the right of way available to put a right turn lane in there. We could do that. This concept would be the most inexpensive way to do this, but when the bank was developed, we got the right of way.
These are just some concepts. We can put in the right turn lane. That was the original idea with the RFQs we’re going to put out for the two intersections. (We are) kind of wanting to get everybody’s thoughts tonight.”
Councilman Matt Herman said one of his concerns about the Florence/Trekell concept is “you have these two southbound lanes coming up and then right at Eighth Street it just goes down to one straight south and then the left turn to east. How do you transition that? I see you can get to the left turn lane from the inside southbound lane, but you still have that lane continuing and it just kind of funnels. I’m just afraid people are going to go and then have to make a quick decision.”
Eitel responded, “On the pavement we would say, ‘through traffic merge right.’ We’d have signs up. And there are some stripes. We could stripe out some things, too, that would show.”
Councilman Karl Montoya asked how traffic would be affected south of Florence when a driver wants to make a left turn into that shopping area.
“That’s where traffic queues up and backs up,” he said. “Does that guy have to wait until the light clears? How much of a problem is that going to create for your intersection? It’s a problem right now and you’re reducing it from two lanes to one. Has there been much thought on that?”
Eitel responded, “One of the problems is, too bad that driveway’s there. It’s hard to pull into.”
But it is there, Montoya said.
Eitel replied, “We just didn’t feel, in looking at the traffic counts, that right now the traffic’s going through. That would be an issue where it would back up onto Florence.”
Montoya said he drives the route every day.
“I go south, and it is a big deal,” he continued. “I just feel that’s going to be a big bottleneck through the intersection, so maybe take a better look at that.”
Councilwoman Mary Kortsen said she would like to see it configured as two lanes with a turn lane for the shopping area.
“I’ve never seen more than three cars trying to turn into that mall at one time, so you could have something that would accommodate at least two vehicles to wait and then you don’t have that,” she said.
Eitel responded, “This is just kind of a concept to show you tonight. When we hire the consultant to do the design, they’ll look more at this (and) we can see the results.”
The full report, with the presentation, charts and diagrams, is posted at www.haroldkitching.com/special
