Monumenting a "centerline" with a roundabout

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dedkad
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Monumenting a "centerline" with a roundabout

Postby dedkad » Thu May 10, 2018 7:29 am

I'm wondering what other jurisdictions are doing when it comes to monumenting a "centerline" on a road that has an offset roundabout. The approach legs to the roundabout start curving and the curves are not concentric on one side of the street to the other, so there isn't really a true centerline to monument. The PIP's will have a construction centerline and that is the line that will most likely be monumented, but even trying to figure out where best to place that construction centerline is confusing. I've attached a sketch of what we're working with and the possible solution.
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RAM
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Re: Monumenting a "centerline" with a roundabout

Postby RAM » Thu May 10, 2018 7:35 am

I would use reference mon's with ties. Here we only monument the R/W and with a map, parcel or R/S, show all dim. necessary to calc the centerline. Therefore anyone can recreate the intent. Keeps surveyors out of the street.

so I would set reference mon's and file a map.

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Warren Smith
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Re: Monumenting a "centerline" with a roundabout

Postby Warren Smith » Thu May 10, 2018 7:47 am

I agree with Russ. Here in Tuolumne County, centerline mons are rare - for the same reason, and the fact that paving is rarely centered in the right of way.
Warren D. Smith, LS 4842
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Tuolumne County

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Peter Ehlert
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Re: Monumenting a "centerline" with a roundabout

Postby Peter Ehlert » Thu May 10, 2018 8:49 am

I agree, there is no need for surveyors to go out in the traffic... are those Islands actually safe to work in? Depends on traffic speed and volume I guess. I prefer well monuments completely out of the traffic, perhaps in the sidewalks is better... unless it is super urban and foot traffic would obscure line of site observation.
Peter Ehlert

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E_Page
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Re: Monumenting a "centerline" with a roundabout

Postby E_Page » Thu May 10, 2018 11:16 am

Unless this is some architect's concept of the ultimate street configuration, there is probably a design centerline for the E-W street and for the N-S street/commercial driveway. If it doesn't exist with adequate dimensions on a plan, it does in the engineer's CAD drawing. Assuming it's actually a designed alingment as opposed to a conceptualized one, it also appears that the center of island, being the CL-intx may also be a PRC for both the E-W and N-S alignments and that much of the design CL would fall on median.

I believe that it's a very good idea to bear in mind the safety of future surveyors at this location, and therefore agree for that reason with the others about monumenting the RW.

But I also know that monuments at the RW are far more likely to get disturbed or destroyed as the contractors for both the PW project and those for the private developers of adjacent properties work over the same ground. After the development occurs, missing and overly discrepant RW monuments are almost certain in a location like this. For that reason, I like to have CL monuments to verify and explain the discrepancies between RW monument which are almost certain to exist to an extent to perplex future surveyors once all the development is complete.

Most PW contractors have been pretty well conditioned to make at least half-hearted attempts to avoid disturbing CL control points. Where they fall in the median, other than crossing lanes to get there, it would keep future surveyors out of traffic.

I have nothing against monumenting the RW and hoping the positions survive the development, but I would also monument the center of the island (assuming it is also CL-int) and the beginning of each of the design CL curves entering the intersection area. If it's an either/or situation and this is expected to be a fairly high traffic location, I would advocate for CL mons where they are on medians and out of direct traffic locations, and RW mons where the CL locations would be within traffic lanes.
Evan Page, PLS
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Proud7191
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Re: Monumenting a "centerline" with a roundabout

Postby Proud7191 » Fri May 11, 2018 7:45 am

Centerline is quickly becoming a thing of the past along major roads (opposed to internal subdivision streets)since the use of CAD. I personally keep arguing for the simplicity of a centerline strip take but as street designs are becoming less and less concentric and r/w is more and more expensive to acquire so I find my self writing more metes and bound takes along the r/w with all the goofy little curves and reverse curves at the back of walk for the engineers.
In order to have long lasting monumentation I map and offset my monuments a couple of feet into the improvements (Lead and tag in sidewalk or curb) so they have the best chance of surviving the years. I find that engineers are still being taught they need a "centerline"when designing when none of their improvements are concentric to it and their calls from the "centerline" are severely lacking on the plans forcing the need to use the cad even though the specs still read "only the plans and spec's will control the construction" :) Jp

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Steve Martin
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Re: Monumenting a "centerline" with a roundabout

Postby Steve Martin » Mon May 14, 2018 11:30 am

I worked on a road improvement project when I was at the County of San Diego, where due to the development of an Indian gaming casino, the old country road had become a virtual freeway. At the time of the preliminary design survey in the early 1990's, the road was 2 or 3 lanes with two lanes uphill and one downhill. The old centerline monuments were in the middle of the fast lane uphill and it was quite exciting to dig those up and tie them in.

Once the improvements were finally complete, we decided to show an alignment for the new centerline on a Record of Survey, but not put monuments out where no one could safely access them. What we did was show the coordinated alignment, control point coordinates, set new control points on top of the storm drain inlet boxes, and showed the station and offset to the new coordinated centerline. The theory being that most surveyors can work with an alignment and do not have to actually occupy a centerline to retrace it.

ROS 19715 in case anyone is interested.

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land butcher
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Re: Monumenting a "centerline" with a roundabout

Postby land butcher » Thu May 17, 2018 11:04 am

Steve Martin wrote:Once the improvements were finally complete, we decided to show an alignment for the new centerline on a Record of Survey, but not put monuments out where no one could safely access them. What we did was show the coordinated alignment, control point coordinates, set new control points on top of the storm drain inlet boxes, and showed the station and offset to the new coordinated centerline. The theory being that most surveyors can work with an alignment and do not have to actually occupy a centerline to retrace it.

ROS 19715 in case anyone is interested.


I really like that idea. As long as there are a lot of CPs.

In looking at the roundabout sketch, it appears there are pedestrian crossings, if so doesn't that counter act the purpose of a roundabout, and put pedestrians at risk crossing without a traffic signal?

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scarpa
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Re: Monumenting a "centerline" with a roundabout

Postby scarpa » Mon May 21, 2018 5:11 pm

LB: I have seen roundabouts with pedestrian crosswalk work quite well. Any vehicle entering the roundabout yields to the vehicles currently in the roundabout. All vehicles yield to pedestrians whether entering or exiting. It is no different than a right turn onto a road with a traffic light island and pedestrian crosswalk; vehicle always yields to pedestrian.

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land butcher
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Re: Monumenting a "centerline" with a roundabout

Postby land butcher » Wed May 23, 2018 1:11 pm

To me having to stop for pedestrians defeats the purpose of having a roundabout. The traffic circle in Long Beach was built in 1930 and rebuilt in 1993 and I can't remember any stop signs at the entrances, might have been yield signs and no pedestrian crossings.
The one in Orange has ped crossings but then traffic is only going about 25mph but peds really mess up the flow.

In France the traffic entering the traffic circle has the right of way and Paris is full of them.

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Peter Ehlert
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Re: Monumenting a "centerline" with a roundabout

Postby Peter Ehlert » Wed May 23, 2018 2:29 pm

The only ones I am vaguely familiar with are the 4 on Paseo de los Heroes in Tijuana.
32°31'29.00"N 117° 1'3.46"W https://www.google.com/maps/place/32%C2 ... 17.0176278
All are signalized, with pedestrian crossings. They seem to work well, especially considering the peak traffic counts. And great place for statues. I don't know the "driving rules", it is kinda intuitive... except for the landscaping and statues I dislike them.
Peter Ehlert


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