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Curb (4") in front of Concrete Barrier

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


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

  • Permanent Concrete Barriers
  • Traversable Features
Other Keywords none
Date September 28, 2015
Attachment MnDOT Curb Types 4 inch.pdf

Response 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

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