Very Basic Traffic Questions 2

[joengr]

Hello,

I have been given the task to address a 2 lane road with a continuous turning lane in the center of the road. The turning lane is a 2 way left turn lane. I have been told to remove the center turn lane in all areas where it is not completely necessary. I am defining necessary to mean I keep the turn lane at intersections and in front of major businesses. I have been reviewing the AASHTO Green Book and MUTCD Manual for information about tapers and medians and transition lanes but I feel like I am just grabbing bits of information randomly and trying to piece it together. Am I going about this the right way or is there some sort of formal process to address re-doing lane markings and stripings?

Thanks

 

[Debaser]

Well, you could look at each junction in turn and assess its capacity and determine whether removing the left-turn lane will cause any unacceptable blocking of the mainline traffic. If so, keep the lane. I would suggest this would result in the absolute minimum level of provision.

Then, see if there are any other intersections where safety may be compromised by removing the lane.

Finally are there any junctions leading to areas which may undergo development soon (unlikely but you never know) and where that committed development may cause the junction to go over capacity? Will yuo remove the lane only for it to be reinstated 6 months down the line?

This is by no means exhaustive but gives you a guide as to whether you can justify the left turn lane provision or not.

 

[ACtrafficengr]

By remove, do you mean physically remove the lane and narrow the pavement? Would cross-hatching it as a flush median be an option?

What is the justification for removing it? It seems to me that the cost of maintaining the pavement would be less than the cost to remove it.

Are you trying to get stormwater credits to avoid mitigation of areas where more impervious area is needed?

"...students of traffic are beginning to realize the false economy of mechanically controlled traffic, and hand work by trained officers will again prevail." - Wm. Phelps Eno, ca. 1928

"I'm searching for the questions, so my answers will make sense." - Stephen Brust

 

[joengr]

Debaser - I will leave the turning lane at each intersection. No future development will take place in the area very old infrastructure and a depressed economic environment. The main purpose of this endeavor is to remove the center turning lane between where there is not an intersection in efforts to widen each lane and increase an area of travel.

ACtrafficengr - The physical pavement dimensions will not change, only the location of the striping will be altered. This is in efforts to widen the area of travel for both north bound and south bound traffic.

 

[joengr]

Sorry, here is the post again; this time with less typos:

Debaser - I will leave the turning lane at each intersection. No future development will take place in the area due to very old infrastructure and a depressed economic environment. The main purpose of this endeavor is to remove the center turning lane where there is not an intersection in efforts to widen each lane and increase an area of travel.

ACtrafficengr - The physical pavement dimensions will not change, only the location of the striping will be altered. This is in efforts to widen the area of travel for both north-bound and south-bound traffic.

 

[francesca]

This looks like a prime opportunity to add utility to the road -- e.g. bike lanes, wide sidewalk, etc. Paint is cheaper, but not as nice for the users.

http://en.wikipedia.org/wiki/Road_diet

 

[ACtrafficengr]

What safety or operational problem are you trying to solve? How does removing the center turn lane address it?

"...students of traffic are beginning to realize the false economy of mechanically controlled traffic, and hand work by trained officers will again prevail." - Wm. Phelps Eno, ca. 1928

"I'm searching for the questions, so my answers will make sense." - Stephen Brust

 

[Debaser]

I will leave the turning lane at each intersection...The main purpose of this endeavor is to remove the center turning lane where there is not an intersection in efforts to widen each lane and increase an area of travel.

I'd be wary of what you'll be left with after doing this. I'm envisaging, either a very wide single lane in each direction, with occasional left-turn lanes developed at the junctions, or perhaps two ahead lanes in one direction (the busier?), one of which then changes to become a left-turn lane at some point.

The first layout wouldn't have much capacity benefit over the existing, except perhaps allowing for easier overtaking manoeuvres, and the second layout could result in some unsafe merging/weaving manoeuvres wherever lane 2 became a turning lane.

 

[joengr]

Cars tend to park along the lane edge limiting the travel width. It was decided that the middle lane is unnecessary at certain locations and should be removed in order to increase the travel width of the lanes here. I personally don't believe the problem here is the geometric layout of the road but lack of enforcement on illegally parked cars, but that decision is above me.

 

[ACtrafficengr]

18 ft wide travel lanes will lead to other problems. I'd either stripe shoulders/bike lanes, or, rather than fighting the parking, stripe it as two through lanes and a parking lane.

Could you post a Google maps link? Maybe then we could provide more concrete advice.

"...students of traffic are beginning to realize the false economy of mechanically controlled traffic, and hand work by trained officers will again prevail." - Wm. Phelps Eno, ca. 1928

"I'm searching for the questions, so my answers will make sense." - Stephen Brust

 

[civilman72]

With regards to your original question about design of tapers and turn lanes - your State DOT should have these design details. The DOT design standards may not be applicable to this road's jurisdiction, but it may be a good place to start. In my experience, most local municipalities do not include auxilary turn lane design requirements in their individual road standards.