Rollover curb v.s. barrier curb

[jdogg03]

Hello my fellow engineers.

I am doing research for an argument over barrier curbs v.s. rollover curbs in subdivisions. Apparantly a memeber of our Council is a contractor and favor rollover curbs, but our ordinance and standards show the City using standard 6" barrier type curbs . From a contractors point it is simple to build and less time consuming. Once poured, the private drive is "tied" to it and that is it. From and engineering standpoint we prefer the aesthetic and safer passage onto private property and protection against pedestrians walking near the curb on the sidewalk. Also I think the ADA favors barrier type curbs, could someone confirm?
To make a long story short, what are your takes on rollover v.s barrier curbs and do you know of any references on the subject? IF so could you please direct me to them.

 

[Qshake]

From my perspective, our neighborhood is full of the 6" barrier.

However, looking back on the neighborhood where I grew up there is predominantly rollovers.

Aestetically, neither really stand out. I've never thought about it until now. I do understand the arguement of easier to construct and from an economic viewpoint I would favor that advantage if it were my neighborhood council.

Just my thoughts. I hope others weigh in as well.

 

[ACtrafficengr]

By rollover curb, do you mean a mountable curb for the full length of the blick, whith no drop curb for the driveway?

As far as ADA goes, I think they're more interested in having a drop curb whereever a pedestrian may want to cross the street, than what type of curb is used between crossing points.

"Barrier" curb offers more discouragement than prevention of vehicles entering the sidewalk. It is said to be fairly ineffective at redirecting errant vehicles. That's why many agencies call it "non-mountable" or "verticle face" now rather than "barrier." On the other hand, if you don't want people parking on the sidewalk, use non-mountable curb.

 

[jdogg03]

QSHAKE, I appreciate your thoughts. Everything you have said is true, especially from the contractor's view. As well LTAP, I feel you as well. You were correct in the definitions of the terms I used.
I guess the bottom line is what "standard drawings" we are using as far as the type of curbs. It seems as there s no real technical data anywhere that favors one over the other. We just don't want the City Council to change what we have been doing or have adopted simply because a member is a contractor.
Anyway thank you guyes.

 

[TVE]

This issue has come up several times in our office, mainly because of the fact that on some projects, my bosses are also the developers in addition to being the engineers. The arguements here go like this:

1) Barrier curb does a better job of keeping vehicles on the street but requires curb cuts at every driveway which can add up cost wise. In fact, builders will mention the fact that they have to pay to cut the curb for the driveways when negotiating the price they will pay for the lots. Not to mention that if the cuts aren't done nicely, the result can be less than appealing.

2) Mountable curbs cost a bit more up front (based on Ontario Provincial Standard Drawings for barrier and mountable curbs) but by eliminating the need for curb cuts, they end result looks much more attractive. Not to mention, you can charge a bit more for the lot given that the builder won't need to pay for a curb cut.

Which curb is actually better? Best answer I have is "personal preference". Of course, its the personal preference of the person at the top of the approval chain that generally ends up winning.

David Dietrich
Thames Valley Engineering

 

[IRstuff]

There's a couple of pedestrian safety issues, but they straddle the question:

> Regular curbs with driveway cuts; I've personally twisted my ankle more than once when not paying attention to where I was stepping and stepped into a cutout.

> The mountable curbs are of a similar vein in the dark, where the edge of the curb is not very visible, so you could wind up stepping down when not expecting it.

TTFN

 

[KRSServices]

Many standards I have drafted and had the pleasure of designing against were along these lines:

In residential subdivisions where the maximum density was equivalent to single family and duplex units, the curbing was to be low profile rolled curb. There was not any requirement for curb cuts and the homeowner could construct a driveway of any width desired.

On collector designated roads and commercial areas, the driveway accesses tend to be more restricted in terms of location, and therefore one easy way to facilitate this is with the 6", 8" or 10" barrier curbing.

In terms of cost, the barrier curb requires slightly more concrete per linear meter, however when slip forming, both are quite expedient relative to time and cost.

KRS Services

http://www.krs-services.com

 

[jdogg03]

Thank you all for your comments. Have a nice day.

 

[PELS]

My experience has been that it comes down to personal preference of the jurisdiction, but home builders prefer rolled curb over vertical curb.

From a cost standpoint, most curb & gutter contractors around here (northern California) use extruded curbs so the labor cost differences should be minimal. The quantity of concrete is higher with the vertical/barrier curbs however, therefore the cost is higher.

Additionally, if barrier curbs are used, you must either determine the driveway location in advance of the house selection and build driveway cuts into the C&G, or you pour vertical curb throughout and when the house and driveway determination is made, you remove a section of vertical curb and pour the driveway cut. Not very cost efficient.

Furthermore, many home builders offer choices of 2-car, 3-car and sometimes 4-car garages. You offer more flexibility and cost savings to the builder if rolled curb is used versus barrier curb because the driveways can be placed anywhere along the lot frontage. This also offers flexibiltiy to the builders who offer their buyers a choice of right-hand or left-hand house layouts of the same floorplan. With vertical curb and pre-determined driveway cuts, you do not have this flexibility.

What we are seeing jurisdictions around here do is require the vertical curbs on the major collector streets where the speed limits are higher and the chances of vehicles running off the pavement is higher. Then, on the local residential streets, rolled curb is allowed for the reasons stated above.

 

[jdogg03]

Great info PELS. I also think that it all boils down to individual preferences and whatever standards the City has adopted.
Versatility is the main factor along with no proven technical data to rule out why rollover cubs CAN'T be used. Well I guess we will just have to be ready to accept the fact that whatever the Council decides on we will have to use.
Thanks.

 

[ACtrafficengr]

I like the idea PELS and KRS mentioned, of linking curb type to access management - allowing mountable curb on local and neighborhood streets, but requiring barrier curb on arterials. Except, of course, that high speed roads should not be curbed.

 

[slots]

Remember that curbs (and gutter) also serve a drainage function. It may not seem significant, but the height of curb, road cross slope, and flowline grade define an important hydraulic element in urban drainage systems. Drainage should be considered in addition to aesthetics, traffic control, costs, and the owner/municipal preferences. (Note that the same curb height for barrier and mountable curbs may entail different concrete quatities and forming costs. Driveway cuts, and aprons also need to allow for controlled drainage away from the property.)