New Mexico Administrative Code › Title 18 - TRANSPORTATION AND HIGHWAYS › Chapter 31 - CLASSIFICATION AND DESIGN STANDARDS FOR HIGHWAYS › Part 6 - STATE HIGHWAY ACCESS MANAGEMENT REQUIREMENTS › Section 18.31.6.17 - SPEED-CHANGE LANE REQUIREMENTS

Current through Register Vol. 35, No. 13, July 16, 2024
A.
Purpose:
This section defines the criteria for determining where
				speed-change lanes are required along non-access controlled and
				controlled-access state highways that provide access via at-grade
				intersections. Application guidelines for speed-change lanes on
				controlled-access interstate highways and freeways, which provide access
				exclusively by grade-separated interchanges, are also provided; however,
				specific criteria for speed-change lanes on grade-separated highway facilities
				are not explicitly defined (see Subsection C of 18.31.6.17 NMAC).
B.
State highways with at-grade
				intersections:
At unsignalized at-grade intersections, four types of
				speed-change lanes are used including left-turn deceleration lanes, right-turn
				deceleration lanes, left-turn acceleration lanes, and right-turn acceleration
				lanes. At signalized at-grade intersections, three types of speed-change lanes
				are used including exclusive left-turn lanes, exclusive right-turn lanes, and
				right-turn acceleration lanes.
(1) Schematic
				illustrations: Illustrations of left-turn and right-turn speed-change lanes can
				be found in the appendix of the
state access management
				manual
.
(2) Design period:
				The need for speed-change lanes should be assessed using the hourly traffic
				volumes derived for the traffic study implementation year with the proposed
				development, or based on the future year traffic forecasts developed for a
				highway improvement project.
(3)
				General criteria:
(a) Speed-change lanes may
				be required by the department at unsignalized or signalized access points where
				specific public safety and traffic operation concerns are identified and
				documented.
(b) Left-turn
				acceleration and deceleration lanes should not overlap. Preference should be
				given to the left-turn deceleration lane. Alternative treatments to providing a
				left-turn acceleration lane may be considered when this situation arises such
				as providing traffic signal control or restricting the left-turn movement from
				the cross street. Alternative treatments require approval by the district
				traffic engineer.
(c) Where two
				access points have right-turn speed-change lanes that overlap, or are in close
				proximity but do not overlap, a continuous ingress/egress lane may be
				established between the access points to improve roadway consistency, safety,
				and to maintain roadway edge continuity.
(d) If the design of an access facility
				crosses two different speed zones, the speed-change lane design should be based
				upon the applicable speed limit. The applicable speed for a deceleration lane
				is the posted speed limit at the beginning of the deceleration lane. The
				applicable speed for an acceleration lane is the posted speed limit at the end
				of the acceleration lane.
(e)
				Acceleration lanes should only be used where sufficient acceleration length can
				be provided.
(f) On multi-lane
				highways, the directional hourly traffic volume, or directional split, should
				be determined based on actual traffic count data. It may be assumed that
				traffic is equally divided among the mainline travel lanes when traffic count
				data are not available.
(4) Unsignalized Intersections: In addition
				to the location of the roadway (urban or rural), the three primary factors used
				to determine the need for a speed-change lane at an unsignalized at-grade
				access are highway travel speed, directional traffic volume per lane, and
				turning traffic volume. Sight distance conditions, level of service, and
				roadway geometry should also be examined when determining the need for
				speed-change lanes.
(a) Urban conditions: The
				need for left-turn and right-turn deceleration lanes on urban state highways
				should be determined based on the criteria in tables 17.B-1 and 17.B-2.
				right-turn acceleration lanes may be required on urban state highways with
				posted speed limits greater than 40 mph where an acceleration lane is necessary
				for public safety and traffic operations based upon site and roadway specific
				conditions. Left-turn acceleration lanes may be required on urban state
				highways with posted speed limits greater than 45 mph where an acceleration
				lane is necessary for public safety and traffic operations based upon site and
				roadway specific conditions.
(b)
				Rural conditions: The need for left-turn and right-turn deceleration lanes on
				rural state highways should be determined based on the criteria in tables
				17.B-3 through 17.B-6. right-turn acceleration lanes may be required on rural
				state highways with posted speed limits greater than 40 mph where an
				acceleration lane is necessary for public safety and traffic operations based
				upon site and roadway specific conditions. Left-turn acceleration lanes may be
				required on rural state highways with posted speed limits greater than 45 mph
				where an acceleration lane is necessary for public safety and traffic
				operations based upon site and roadway specific conditions.
(5) Signalized intersections: The
				use of speed-change lanes at signalized intersections is generally consistent
				for all access categories, urban and rural. Guidelines for determining the need
				for speed-change lanes at signalized intersections can be found in Section 17
				of the
state access management manual
.