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 18.31.6.18 - ACCESS LOCATION AND DESIGN STANDARDS
Current through Register Vol. 35, No. 18, September 24, 2024
The location and design of access points along state highway facilities shall be in accordance with standards established by the department. These standards are defined below and are expounded on in Section 18 of the state access management manual. Where specific design criteria are not provided in 18.31.6.18 NMAC, the design approach should be based on nationally accepted standards and shall be consistent with department specifications.
A. General: The department has developed these standards to provide guidance for the location and design of access points along state highways, specifically for those highways in access categories (provided in Section 18.31.6.10 NMAC). These criteria are based upon established design standards meant to protect public safety, to maintain safe and smooth-flowing traffic operations, and to preserve the intended function of all state highway facilities.
B. Access location: Access points should be located along state highways to minimize turning movement conflicts between adjacent access facilities, and to provide adequate separation of conflicts for oncoming motorists. Stopping sight distance and intersection area of influence should be considered in determining access point locations.
C. Access spacing:
D. Median openings: New median openings on state highways with non-traversable medians should not be allowed unless a traffic engineering evaluation analyzing all related traffic and safety issues is prepared and approved by the department. Median openings at intersections or full-access driveways should be spaced with a minimum frequency based upon the access category and posted speed of the highway.
E. Selection of design vehicle: The design vehicle should be used to determine the geometric characteristics of a roadside access or median opening, and to define the required design components for the adjacent highway. This vehicle should be the largest vehicle that is expected to access the site on a daily basis. Selection of the design vehicle is subject to the approval of the district traffic engineer.
F. Sight distance: Sight distance at all access locations shall be adequate to provide safe operating conditions for the motoring public. An access permit should not be issued unless adequate stopping sight distances are provided for motorists passing the access, and adequate entering and crossing sight distances are provided for motorists using the access. The permittee shall maintain adequate, unobstructed sight distance in both directions from the access. Any potentially obstructing objects such as but not limited to advertising signs, structures, trees and bushes, shall be designed, placed and maintained at a height not to interfere with the sight distances needed by any vehicle using the access. Roadway reconstruction may be required to provide adequate sight distance.
G. Access horizontal alignment: The access centerline should be perpendicular to the state highway centerline and extend tangentially for a minimum distance of 40 feet beyond the near-side edge line. An acute angle between 75 degrees and 90 degrees may be permitted if significant physical constraints exist. Acute angles less than 75 degrees shall require special approval of the department.
H. Access radius: The access radius should be designed to accommodate the design vehicle expected to use the access on a daily basis. Access radii apply to driveways that are not urban section driveway cuts.
I. Driveway width: The width of a driveway should be measured exclusive of radii or tapers. Driveway widths should vary by design vehicle. All two-way driveways should accommodate a concurrent entering and exiting design vehicle, including the design vehicle's off-tracking.
J. Access connection depth: The access connection depth should be designed to facilitate the movement of vehicles off the highway to prevent the queuing of vehicles on the traveled way. An access shall not be approved for parking areas that require backing maneuvers within state highway right-of-way. All off-street parking areas must include on-site maneuvering areas and aisles to permit vehicles to enter and exit the site in forward drive without hesitation.
K. Speed change lanes: Design specifications for speed change lanes are provided in Section 18 of the state access management manual. Schematic illustrations of speed-change lanes are included in the appendix of the state access management manual.
L. Median design for turn lane installation: Medians should be designed to accommodate the largest design vehicle anticipated to use the access, and may provide either partial or full access to a site. Where a single left-turn lane is necessary along a state highway, a minimum median width of 16 feet should be provided. Positive channelization should be provided for all median openings. Median paving should be full depth and match the pavement section design of the existing roadway. The installation of a median opening should not reduce the conveyance or storage capacity of the median, pertinent to its drainage function within the highway section.
M. Setbacks: Improvements on public or private property adjacent to the right-of-way should be located so that parking, stopping, and maneuvering of vehicles within the highway right-of-way will not occur.
N. Access vertical alignment: The vertical alignment of all access locations should be designed to minimize vehicle bounce and prevent high-centering of vehicles with a maximum clearance of four inches. The maximum grade for a driveway should be ten percent for a low volume residential driveway and eight percent for all other access locations. Steeper access drives require special department approval. A level area (maximum two percent grade) 20 feet in length should be provided at each access to ensure proper sight distance from the access.
O. Roadside safety: Careful consideration shall be given to the roadside clear zone. The permittee shall provide adequate clear zones. The roadside clear zone should be designed per the AASHTO roadside design guide and applicable department standards.
P. Non-motorized considerations: Access designs should provide for the safe movement of all right-of-way users, including but not limited to pedestrians, bicyclists, equestrian and the handicapped. Where non-motorized facilities cross an access point, such as bicycle trails, appropriate modifications should be made to maintain safe operations for both facilities.
Q. Lighting: Where lighting is required at an access point, the lighting design shall comply with Department and AASHTO standards and the Night Sky Protection Act (Sections 74-12-1 NMSA 1978 through 74-12-11 NMSA 1978). The lighting design shall use full cut-off fixtures, and be consistent with AD 226, roadway lighting.
R. Drainage: Adequate drainage within state highway right-of-way shall be maintained at all access locations. Drainage of roadside ditches shall not be altered or impeded, and the applicant shall provide suitable and approved drainage structures as required by the department. All site drainage shall be collected prior to entering state highway right-of-way. Site drainage shall not be permitted to drain into state right-of-way without written approval of the department. Drainage mitigation design shall be in accordance with administrative memorandum 221, drainage design criteria, and the department drainage manual. Access permit applicants shall submit drainage analysis documentation to the department prior to changing site drainage conditions.
S. Right-of-way fencing: Driveways shall not be permitted through an existing right-of-way fence, the continuation of which is necessary for the safety of the traveling public, unless the applicant first agrees in writing to construct and maintain a gate or a cattle guard and additional fence in good repair and to keep the gate closed to livestock. The department shall determine whether a gate or cattle guard is required. All new fencing along a state highway shall be constructed so that clear sight triangles are provided for ingressing or egressing vehicles. This may require an offset from the right-of-way line to meet the minimum clear site triangles, on a case by case basis.
T. Mailboxes: Mailboxes installed within the state highway right-of-way shall be constructed in conformance with the rules and regulations of the U.S. Postal service and the design standards of the department. AASHTO's a guide for erecting mailboxes on highways, should also be used for the location and design of mailbox installations.
U. Utilities: All utilities located within the state highway right-of-way shall comply with the department's utility accommodations Policy and 17.4.2. NMAC.
V. Environmental review: As may be required by law.