AD-241 Department Drop-Off Guidelines - New Mexico Department ...

NEW MEXICO DEPARTMENT OF TRANSPORTATION
Pavement Drop-Off for Construction Work Zones
AUTHORITY: 1.00 N/A
AD 241
08/01/10
________________________________
Alvin C. Dominguez, P.E., Cabinet Secretary
Supersedes Administrative Directive No. 241 dated October 1,
2005
PURPOSE: 2.00 To provide guidelines for addressing pavement drop-offs that
may occur in construction work zones.
DEFINITIONS: 3.00 "Construction Work Zones" are defined as the area where traffic
control is provided to maintain traffic flow during pavement
preservation, rehabilitation, reconstruction, milling or shoulder
widening.
DIRECTIVE: 4.00 The New Mexico Department of Transportation publication,
"Pavement Drop-off Guidelines for Construction Work Zones",
shall be used for all highway projects involving construction work
zones.
PROCEDURES: 5.00 N/A
CROSS
REFERENCE: 6.00 N/A
AD 241 Page 1

PURPOSE
New Mexico Department of Transportation
PAVEMENT DROP-OFF GUIDELINES FOR CONSTRUCTION WORK ZONES
This document is introduced to provide guidance for addressing pavement drop-offs that may
occur in construction work zones.
BACKGROUND
Pavement drop-offs occur when the longitudinal edge of the travel line is not flush with the
adjacent existing surface. Pavement drop-offs can be created in construction work zones.
Construction work zones are defined as the area where traffic control is provided to maintain
traffic during pavement preservation, rehabilitation, reconstruction, milling and shoulder widening.
APPLICATION
This guideline is applicable to all highway construction work zones. To the extent possible, the
following guidance should be used in the development of traffic control plans for all highway
projects involving construction work zones. On very high volume roads (VHVR) where speeds
are thirty miles per hour (30 mph) or less, or on very low volume roads (VLVR) where average
daily traffic is estimated below 500 vehicles, these guidelines should be incorporated where
practical.
The following are example cases where a pavement drop-off may occur: (There may be
situations that do not exactly fit one of the examples cases. In those situations, the case that
most closely resembles the situation should be used.)
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PAVEMENT DROP-OFF CASES
CASE I - Activities Within the Travel Lane Such as Milling or Overlay Operations.
A maximum 1.5 in. vertical drop-off between adjacent surfaces will be allowed at the centerline, or
lane lines without treatment. When the drop-off is greater than 1.5 in., a fillet with a slope of 6:1
or flatter shall be provided during non-working hours. The work shall be scheduled to result in not
more than one day operation of exposed longitudinal joint between adjacent surfaces.
CASE II - Areas Adjacent to the Existing Travel Lane with Buffer Zones Less than 6 ft. In Width.
A buffer zone is defined as any smooth, traversable surface that does not contain any obstruction
or drop-offs.
1) For travel lane widths within construction work zones of 11 ft. or more:
a) A slope of 3:1 or flatter should be constructed whenever possible; however, a
maximum 3 in. drop-off will be allowed without any special treatment. Vertical panels
or other delineation devices shall be provided to delineate the drop-off.
b) Drop-offs greater than 3 in. that are exposed to traffic during non-working hours shall
be protected by a fillet (3:1 or flatter slopes) with delineation by drums, vertical panels,
or other delineation devises. If fillet of less than 3:1 slope is not achievable, positive
barrier (concrete wall barrier or approved equal) protection should be used.
For travel lane widths within construction work zones of less than 11 ft., the procedure outlines
under exceptions will apply.
CASE III - Areas Adjacent to the Existing Travel Lane with Buffer Zones 6 ft. or More in Width.
1) A slope of 3:1 or flatter should be constructed whenever possible.
2) In those cases where a 3:1 or flatter slope is not possible, the following shall apply:
a) For drop-offs less than 1 ft., vertical panels or other delineation devices shall be used.
For drop-offs in excess of 1 ft., Type "B" drums at a spacing approved by the District Traffic
Engineer or design team shall be used.
CASE IV - Point Drop-offs Such as Drop Inlets and CBC Ends.
When this type of drop-off is present, every effort should be made to place the appropriate
permanent nature, such as guardrail or inlet grates, as soon as possible. The following
temporary measures shall apply:
1) For drop-offs located 6ft. or more from the travel lane, Type "B" drums shall be used to
delineate the hazard.
2) For drop-offs located less than 6 ft. from the travel lane, positive barrier (concrete wall
barrier or approved equal) protection shall be provided. Type "B" drums may be used if
the drop-off will be exposed for less than 24 hours.
EXCEPTIONS
During the development of a traffic control plan of a project, the drop-offs will be reviewed along
with the required traffic control. If the criteria set forth in this guideline cannot be obtained
through reasonable and prudent design practices an exception may be granted. The design team
with the Project Development Engineer (PDE) as the lead member shall discuss the situation and
provide a recommended course of action. The PDE shall initiate action for this to be processed
as a design exception. For District lead projects, the District Technical Support Engineer will be
the lead member.
During the construction phase of a project, the project manager shall contact the Assistant District
Engineer and District Traffic Engineer for guidance when the guideline criteria cannot be met.
They shall provide a recommended course of action along with a change order to the appropriate
Bureau, if required.
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