N.M. Code R. § 18.31.6.17 – Speed-change Lane Requirements

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. (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. (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. (3) General criteria:
  1. (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.
  2. (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.
  3. (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.
  4. (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.
  5. (e) Acceleration lanes should only be used where sufficient acceleration length can be provided.
  6. (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. (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.
  1. (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.
  2. (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. (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.
C. State and interstate highways with grade-separated interchanges: Speed-change lanes are used on controlled-access state and interstate highways at or between grade-separated interchanges. The need for speed-change lanes on grade-separated highway facilities should be determined based on design principles contained in the AASHTO publication a policy on geometric design of highways and streets, and based on detailed traffic operations analyses of the grade-separated facilities according to highway capacity manual methodologies. The need for and function of speed-change lanes should be documented in an interchange access management plan for the interchange (refer to 18.31.6.12 NMAC). Speed-change lanes on grade-separated highway facilities should enable a driver to make the necessary transition between the speed on a ramp and the speed of operation on the mainline highway in a safe and functional manner. Additional guidance is provided in Section 17 of the state access management manual.

Table 17.B-1 Criteria for Deceleration Lanes On Urban Two-lane Highways Turning Volume (vph) LEFT-TURN DECELERATION LANE RIGHT-TURN DECELERATION LANE Minimum Directional Volume in the Through Lane (vphpl) ² Minimum Directional Volume in the Through Lane (vphpl) ²  30 mph 35 to 40 mph 45 to 55 mph  30 mph 35 to 40 mph 45 to 55 mph  5 Not Required Not Required Not Required Not Required Not Required Not Required 5 510 450 330 1,080 610 360 10 390 330 210 700 400 240 15 320 250 150 500 280 170 20 270 200 120 380 210 140 25 230 160 100 300 180 120 30 200 130 Required 250 160 110 35 170 110 Required 220 150 100 40 150 Required Required 200 140 Required 45 130 Required Required 190 Required Required  46 Required Required Required Required Required Required Left-turn Deceleration Lanes are required on Urban Two-lane Highways for the following Left-turn Volumes: Right-turn Deceleration Lanes are required on Urban Two-lane Highways for the following Right-turn Volumes: if !supportLists1. endif 30 mph : 46 vph or more if !supportLists2. endif35 to 40 mph : 36 vph or more if !supportLists3. endif45 to 55 mph : 26 vph or more if !supportLists4. endif 30 mph : 46 vph or more if !supportLists5. endif35 to 40 mph : 41 vph or more if !supportLists6. endif45 to 55 mph : 36 vph or more Notes: if !supportLists1. endifUse linear interpolation for turning volumes between 5 and 45 vph. if !supportLists2. endifThe directional volume in the through lane includes through vehicles and turning vehicles.
(vph)
Minimum Directional Volume in the Through Lane (vphpl) ²
Minimum Directional Volume in the Through Lane (vphpl) ²
 30 mph
35 to 40 mph
45 to 55 mph
 30 mph
35 to 40 mph
45 to 55 mph
 5
Not Required
Not Required
Not Required
Not Required
Not Required
Not Required
5
510
450
330
1,080
610
360
10
390
330
210
700
400
240
15
320
250
150
500
280
170
20
270
200
120
380
210
140
25
230
160
100
300
180
120
30
200
130
Required
250
160
110
35
170
110
Required
220
150
100
40
150
Required
Required
200
140
Required
45
130
Required
Required
190
Required
Required
 46
Required
Required
Required
Required
Required
Required
if !supportLists1. endif 30 mph : 46 vph or more
if !supportLists2. endif35 to 40 mph : 36 vph or more
if !supportLists3. endif45 to 55 mph : 26 vph or more
if !supportLists4. endif 30 mph : 46 vph or more
if !supportLists5. endif35 to 40 mph : 41 vph or more
if !supportLists6. endif45 to 55 mph : 36 vph or more
Notes:
if !supportLists1. endifUse linear interpolation for turning volumes between 5 and 45 vph.
if !supportLists2. endifThe directional volume in the through lane includes through vehicles and turning vehicles.
Table 17.B-2 Criteria for Deceleration Lanes on Urban Multi-lane Highways Turning Volume ¹ (vph) LEFT-TURN DECELERATION LANE RIGHT-TURN DECELERATION LANE Minimum Volume in the Adjacent Through Lane (vphpl) ² Minimum Volume in the Adjacent Through Lane (vphpl) ²  30 mph 35 to 40 mph 45 to 55 mph  30 mph 35 to 40 mph 45 to 55 mph  5 Not Required Not Required Not Required Not Required Not Required Not Required 5 Not Required 490 420 1,200 730 450 10 420 370 300 820 490 320 15 360 290 220 600 350 240 20 310 230 160 460 260 180 25 270 190 130 360 230 150 30 240 160 110 290 200 130 35 210 130 100 260 180 120 40 180 120 Required 240 170 110 45 160 110 Required 220 160 Required 50 140 Required Required 200 Required Required 55 120 Required Required 190 Required Required  56 Required Required Required Required Required Required Left-turn Deceleration Lanes are required on Urban Multi-lane Highways for the following Left-turn Volumes: Right-turn Deceleration Lanes are required on Urban Multi-lane Highways for the following Right-turn Volumes: if !supportLists3. endif 30 mph : 56 vph or more if !supportLists4. endif35 to 40 mph : 46 vph or more if !supportLists5. endif45 to 55 mph : 36 vph or more if !supportLists6. endif 30 mph : 56 vph or more if !supportLists7. endif35 to 40 mph : 46 vph or more if !supportLists8. endif45 to 55 mph : 41 vph or more Notes: if !supportLists1. endifUse linear interpolation for turning volumes between 5 and 55 vph. if !supportLists2. endifThe volume in the adjacent through lane includes through vehicles and turning vehicles.
(vph)
Minimum Volume in the Adjacent Through Lane (vphpl) ²
Minimum Volume in the Adjacent Through Lane (vphpl) ²
 30 mph
35 to 40 mph
45 to 55 mph
 30 mph
35 to 40 mph
45 to 55 mph
 5
Not Required
Not Required
Not Required
Not Required
Not Required
Not Required
5
Not Required
490
420
1,200
730
450
10
420
370
300
820
490
320
15
360
290
220
600
350
240
20
310
230
160
460
260
180
25
270
190
130
360
230
150
30
240
160
110
290
200
130
35
210
130
100
260
180
120
40
180
120
Required
240
170
110
45
160
110
Required
220
160
Required
50
140
Required
Required
200
Required
Required
55
120
Required
Required
190
Required
Required
 56
Required
Required
Required
Required
Required
Required
if !supportLists3. endif 30 mph : 56 vph or more
if !supportLists4. endif35 to 40 mph : 46 vph or more
if !supportLists5. endif45 to 55 mph : 36 vph or more
if !supportLists6. endif 30 mph : 56 vph or more
if !supportLists7. endif35 to 40 mph : 46 vph or more
if !supportLists8. endif45 to 55 mph : 41 vph or more
Notes:
if !supportLists1. endifUse linear interpolation for turning volumes between 5 and 55 vph.
if !supportLists2. endifThe volume in the adjacent through lane includes through vehicles and turning vehicles.
Table 17.B-3 Criteria for Left-Turn Deceleration Lanes on Rural Two-lane Highways Left-Turn Volume ¹ (vph) LEFT-TURN DECELERATION LANE Minimum Directional Volume in Through Lane (vphpl) ²  30 mph 35 to 40 mph 45 to 55 mph  55 mph  5 Not Required Not Required Not Required Not Required 5 400 220 120 60 10 240 140 80 40 15 160 100 60 Required 20 120 80 Required Required 25 100 Required Required Required  26 Required Required Required Required Left-turn Deceleration Lanes are required on Rural Two-lane Highways for the following Left-turn Volumes: if !supportLists1. endif 30 mph : 26 vph or more if !supportLists2. endif35 to 40 mph : 21 vph or more if !supportLists3. endif45 to 55 mph : 16 vph or more if !supportLists4. endif 55 mph : 11 vph or more Notes: Use linear interpolation for left-turn volumes between 5 and 25 vph. The directional volume in the through lane includes through vehicles and turning vehicles.
Left-Turn Volume ¹ (vph)
Minimum Directional Volume in Through Lane (vphpl) ²
 30 mph
35 to 40 mph
45 to 55 mph
 55 mph
 5
Not Required
Not Required
Not Required
Not Required
5
400
220
120
60
10
240
140
80
40
15
160
100
60
Required
20
120
80
Required
Required
25
100
Required
Required
Required
 26
Required
Required
Required
Required
if !supportLists1. endif 30 mph : 26 vph or more
if !supportLists2. endif35 to 40 mph : 21 vph or more
if !supportLists3. endif45 to 55 mph : 16 vph or more
if !supportLists4. endif 55 mph : 11 vph or more
Notes:
Use linear interpolation for left-turn volumes between 5 and 25 vph.
The directional volume in the through lane includes through vehicles and turning vehicles.
Table 17.B-4 Criteria for Left-turn Deceleration Lanes on Rural Multi-lane Highways Left-Turn Volume ¹ (vph) LEFT-TURN DECELERATION LANE Minimum Volume in Adjacent Through Lane (vphpl) ²  30 mph 35 to 40 mph 45 to 55 mph  55 mph  5 Not Required Not Required Not Required Not Required 5 450 310 210 130 10 310 220 130 90 15 240 160 100 70 20 190 130 80 Required 25 150 110 Required Required 30 130 Required Required Required 35 110 Required Required Required  36 Required Required Required Required Left-turn Deceleration Lanes are required on Rural Multi-lane Highways for the following Left-turn Volumes: if !supportLists5. endif 30 mph : 36 vph or more if !supportLists6. endif35 to 40 mph : 26 vph or more if !supportLists7. endif45 to 55 mph : 21 vph or more if !supportLists8. endif 55 mph : 16 vph or more Notes: if !supportLists1. endifUse linear interpolation for left-turn volumes between 5 and 35 vph. if !supportLists2. endifThe volume in the adjacent through lane includes through vehicles and turning vehicles.
Criteria for Left-turn Deceleration Lanes on
Left-Turn Volume ¹ (vph)
Minimum Volume in Adjacent Through Lane (vphpl) ²
 30 mph
35 to 40 mph
45 to 55 mph
 55 mph
 5
Not Required
Not Required
Not Required
Not Required
5
450
310
210
130
10
310
220
130
90
15
240
160
100
70
20
190
130
80
Required
25
150
110
Required
Required
30
130
Required
Required
Required
35
110
Required
Required
Required
 36
Required
Required
Required
Required
if !supportLists5. endif 30 mph : 36 vph or more
if !supportLists6. endif35 to 40 mph : 26 vph or more
if !supportLists7. endif45 to 55 mph : 21 vph or more
if !supportLists8. endif 55 mph : 16 vph or more
Notes:
if !supportLists1. endifUse linear interpolation for left-turn volumes between 5 and 35 vph.
if !supportLists2. endifThe volume in the adjacent through lane includes through vehicles and turning vehicles.
Table 17.B-5 Criteria for Right-Turn Deceleration Lanes on Rural Two-lane Highways Right-Turn Volume ¹ (vph) RIGHT-TURN DECELERATION LANE Minimum Directional Volume in Through Lane (vphpl) ²  30 mph 35 to 40 mph 45 to 55 mph  55 mph  5 Not Required Not Required Not Required Not Required 5 800 460 270 160 10 430 280 170 110 15 290 180 110 80 20 200 140 90 70 25 170 120 80 Required 30 160 110 Required Required  31 Required Required Required Required Right-turn Deceleration Lanes are required on Rural Two-lane Highways for the following Right-turn Volumes: if !supportLists3. endif 30 mph : 31 vph or more if !supportLists4. endif35 to 40 mph : 31 vph or more if !supportLists5. endif45 to 55 mph : 26 vph or more if !supportLists6. endif 55 mph : 21 vph or more Notes: if !supportLists1. endifUse linear interpolation for left-turn volumes between 5 and 30 vph. if !supportLists2. endifThe directional volume in the through lane includes through vehicles and turning vehicles.
Criteria for Right-Turn Deceleration Lanes on
Right-Turn Volume ¹ (vph)
Minimum Directional Volume in Through Lane (vphpl) ²
 30 mph
35 to 40 mph
45 to 55 mph
 55 mph
 5
Not Required
Not Required
Not Required
Not Required
5
800
460
270
160
10
430
280
170
110
15
290
180
110
80
20
200
140
90
70
25
170
120
80
Required
30
160
110
Required
Required
 31
Required
Required
Required
Required
Right-turn Deceleration Lanes are required on Rural Two-lane Highways for the following Right-turn Volumes:
if !supportLists3. endif 30 mph : 31 vph or more
if !supportLists4. endif35 to 40 mph : 31 vph or more
if !supportLists5. endif45 to 55 mph : 26 vph or more
if !supportLists6. endif 55 mph : 21 vph or more
Notes:
if !supportLists1. endifUse linear interpolation for left-turn volumes between 5 and 30 vph.
if !supportLists2. endifThe directional volume in the through lane includes through vehicles and turning vehicles.
Table 17.B-6 Criteria for Right-Turn Deceleration Lanes on Rural Multi-lane Highways Right-Turn Volume ¹ (vph) RIGHT-TURN DECELERATION LANE Minimum Volume in Adjacent Through Lane (vphpl) ²  30 mph 35 to 40 mph 45 to 55 mph  55 mph  5 Not Required Not Required Not Required Not Required 5 910 520 310 180 10 520 330 200 130 15 370 220 140 100 20 270 170 110 90 25 220 140 100 Required 30 200 130 90 Required 35 180 120 Required Required  36 Required Required Required Required Right-turn Deceleration Lanes are required on Rural Multi‑lane Highways for the following Right-turn Volumes: if !supportLists3. endif 30 mph : 36 vph or more if !supportLists4. endif35 to 40 mph : 36 vph or more if !supportLists5. endif45 to 55 mph : 31 vph or more if !supportLists6. endif 55 mph : 21 vph or more Notes: if !supportLists1. endifUse linear interpolation for left-turn volumes between 5 and 35 vph. if !supportLists2. endifThe volume in the adjacent through lane includes through vehicles and turning vehicles.
Criteria for Right-Turn Deceleration Lanes on
Right-Turn Volume ¹ (vph)
Minimum Volume in Adjacent Through Lane (vphpl) ²
 30 mph
35 to 40 mph
45 to 55 mph
 55 mph
 5
Not Required
Not Required
Not Required
Not Required
5
910
520
310
180
10
520
330
200
130
15
370
220
140
100
20
270
170
110
90
25
220
140
100
Required
30
200
130
90
Required
35
180
120
Required
Required
 36
Required
Required
Required
Required
Right-turn Deceleration Lanes are required on Rural Multi‑lane Highways for the following Right-turn Volumes:
if !supportLists3. endif 30 mph : 36 vph or more
if !supportLists4. endif35 to 40 mph : 36 vph or more
if !supportLists5. endif45 to 55 mph : 31 vph or more
if !supportLists6. endif 55 mph : 21 vph or more
Notes:
if !supportLists1. endifUse linear interpolation for left-turn volumes between 5 and 35 vph.
if !supportLists2. endifThe volume in the adjacent through lane includes through vehicles and turning vehicles.

[18.31.6.17 NMAC - Rp, 18.31.6.17 NMAC, 6/27/2017]