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Curb (4") in front of Concrete Barrier

Question
State	MN
Description Text	We would like your input regarding on 4” high curbs, particularly with respect to potential vehicle redirection. There is general language in AASHTO Green Book, the Roadside Safety Guide and the Safety Manual, along with the MnDOT RDM, but nothing that I would consider definitive. Many Trunk Highway and Interstate projects have included these raised curb sections adjacent to shoulders, in order to manage snow storage. Typically, these configurations will have a concrete barrier located behind the minimally raised curb section. It has been my understanding that a 4” curb has not been considered to be vertical curb ( with the definition provided in the AASHTO Greenbook ) and the MnDOT Geometrics and/or Safety Office has not identified these as a significant re-directional hazard to vehicles. I would appreciate your insight. Thank You. Minnesota DOT

Question

State

Description Text

We would like your input regarding on 4”
high curbs, particularly with respect to potential vehicle redirection. There
is general language in AASHTO Green Book, the Roadside Safety Guide and the
Safety Manual, along with the MnDOT RDM, but nothing that I would consider
definitive.

Many Trunk Highway and Interstate projects have included
these raised curb sections adjacent to shoulders, in order to manage snow
storage. Typically, these configurations will have a concrete barrier
located behind the minimally raised curb section. It has been my understanding
that a 4” curb has not been considered to be vertical curb ( with the
definition provided in the AASHTO Greenbook ) and the MnDOT Geometrics and/or
Safety Office has not identified these as a significant re-directional hazard
to vehicles.

I would appreciate your insight.

Thank You.

Minnesota DOT

System Performance Evaluation

System Types
Geometric and Traversable Features
Permanent Concrete Barriers

Applications

System Features

Date September 28, 2015
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Attachment MnDOT Curb Types 4 inch.pdf

Response
Response (active)	With respect to the 4" curb alone, there are no issues with traversability or vehicle redirection. Various tests of curbs have been performed that have shown curb heights of 4" are not sufficient to redirect a vehicle nor do they tend to cause vehicle instability on their own. That said, the use of the 4" curb may affect the performance of concrete barrier designs depending on the offset of the curb and geometry of the concrete barrier as curbs adjacent to the barrier may increase vehicle climb and the potential for vehicle instability.

Response

Response
(active)

With respect to the 4" curb alone, there are no issues with traversability or vehicle redirection. Various tests of curbs have been performed that have shown curb heights of 4" are not sufficient to redirect a vehicle nor do they tend to cause vehicle instability on their own.

That said, the use of the 4" curb may affect the performance of concrete barrier designs depending on the offset of the curb and geometry of the concrete barrier as curbs adjacent to the barrier may increase vehicle climb and the potential for vehicle instability.

Date September 30, 2015
Previous Views (178) Favorites (0)