4.7.5 Superelevation Rate on Rural and High-Speed Suburban, Urban, and Urban Core Facilities

Table 4-5
,
Table 4-6
and
Table 4-7
show superelevation rates (maximum 4 percent, 6 percent and 8 percent, respectively) for various design speeds and radii based on
Method 5
 superelevation distribution.
These tables should be used for rural and highspeed suburban, urban, and urban core facilities.
For multi-lane facilities, particularly where wide medians are used, the radius applies to the inside edge of the innermost travel lane.
Table 4-5: Minimum Radii and Superelevation Rates
1
 for High-Speed Suburban and Urban Non-Freeway Facilties, e
max
 = 4%
1, 2
 (Method 5)
Design Speed
e
(%)
15
mph
R(ft)
20
mph
R(ft)
25
mph
R(ft)
30
mph
R(ft)
35
mph
R(ft)
40
mph
R(ft)
45
mph
R(ft)
50
mph
R(ft)
55
mph
R(ft)
60
mph
R(ft)
NC
3,5
(Method 2)
7,220
8,650
10,300
RC
4,5
4,940
5,950
7,080
2.2
4,280
5,180
6,190
2.4
3,690
4,500
5,410
2.6
3,130
3,870
4,700
2.8
2,660
3,310
4,060
3.0
2,290
2,860
3,530
3.2
1,980
2,490
3,090
3.4
1,720
2,170
2,700
3.6
1,480
1,880
2,350
3.8
1,260
1,600
2,010
4.0
926
1,190
1,500
Notes:
  1. Computed using Superelevation Distribution Method 5. See AASHTO’s A Policy on Geometric Design of Highways and Streets for the different types of Superelevation Distribution Methods.
  2. Use of e
    max
    =4% should be limited to high-speed urban and suburban areas. Freeway facilities are excluded from using e
    max
    =4%.
  3. a) The term “NC” (normal crown) represents an equal downward cross-slope, typically 2%, on each side of the axis of rotation.
    b) The minimum curve radii for normal crown are suitable up to 3.0%.
    c) 3.0% normal crown should only be used when 3 or more lanes are sloped in the same direction.
    d) 1.5% or flatter normal crown should only be used for the design of special circumstance, such as table-topping intersections, or the evaluation of existing conditions.
  4. . The term “RC” (reverse crown) represents a curve where the downward, or adverse, cross-slope should be removed by superelevating the entire roadway at the normal cross-slope rate.
  5. For curve radii falling between normal crown and reverse crown, rather than interpolation a superelevation rate equal to the normal crown should typically be used
Table 4-6: Minimum Radii and Superelevation Rates
1
 for Rural and High-Speed Suburban, Urban and-Urban Core Facilities, e
max
 = 6%
Design Speed
e
(%)
15
mph
R (ft)
20
mph
R (ft)
25
mph
R (ft)
30
mph
R (ft)
35
mph
R (ft)
40
mph
R (ft)
45
mph
R (ft)
50
mph
R (ft)
55
mph
R (ft)
60
mph
R (ft)
65
mph
R (ft)
70
mph
R (ft)
75
mph
R (ft)
80
mph
R (ft)
NC
2,4
868
1,580
2,290
3,130
4,100
5,230
6,480
7,870
9,410
11,100
12,600
14,100
15,700
17,400
RC
3,4
614
1,120
1,630
2,240
2,950
3,770
4,680
5,700
6,820
8,060
9,130
10,300
11,500
12,900
2.2
543
991
1,450
2,000
2,630
3,370
4,190
5,100
6,110
7,230
8,200
9,240
10,400
11,600
2.4
482
884
1,300
1,790
2,360
3,030
3,770
4,600
5,520
6,540
7,430
8,380
9,420
10,600
2.6
430
791
1,170
1,610
2,130
2,740
3,420
4,170
5,020
5,950
6,770
7,660
8,620
9,670
2.8
384
709
1,050
1,460
1,930
2,490
3,110
3,800
4,580
5,440
6,200
7,030
7,930
8,910
3.0
341
635
944
1,320
1,760
2,270
2,840
3,480
4,200
4,990
5,710
6,490
7,330
8,260
3.2
300
566
850
1,200
1,600
2,080
2,600
3,200
3,860
4,600
5,280
6,010
6,810
7,680
3.4
256
498
761
1,080
1,460
1,900
2,390
2,940
3,560
4,250
4,890
5,580
6,340
7,180
3.6
209
422
673
972
1,320
1,740
2,190
2,710
3,290
3,940
4,540
5,210
5,930
6,720
3.8
176
358
583
864
1,190
1,590
2,010
2,490
3,040
3,650
4,230
4,860
5,560
6,320
4.0
151
309
511
766
1,070
1,440
1,840
2,300
2,810
3,390
3,950
4,550
5,220
5,950
4.2
131
270
452
684
960
1,310
1,680
2,110
2,590
3,140
3,680
4,270
4,910
5,620
4.4
116
238
402
615
868
1,190
1,540
1,940
2,400
2,920
3,440
4,010
4,630
5,320
4.6
102
212
360
555
788
1,090
1,410
1,780
2,210
2,710
3,220
3,770
4,380
5,040
4.8
91
189
324
502
718
995
1,300
1,640
2,050
2,510
3,000
3,550
4,140
4,790
5.0
82
169
292
456
654
911
1,190
1,510
1,890
2,330
2,800
3,330
3,910
4,550
5.2
73
152
264
413
595
833
1,090
1,390
1,750
2,160
2,610
3,120
3,690
4,320
5.4
65
136
237
373
540
759
995
1,280
1,610
1,990
2,420
2,910
3,460
4,090
5.6
58
121
212
335
487
687
903
1,160
1,470
1,830
2,230
2,700
3,230
3,840
5.8
51
106
186
296
431
611
806
1,040
1,320
1,650
2,020
2,460
2,970
3,560
6.0
39
81
144
231
340
485
643
833
1,060
1,330
1,660
2,040
2,500
3,050
Notes:
  1. Computed using Superelevation Distribution Method 5. See AASHTO’s A Policy on Geometric Design of Highways and Streets for the different types of Superelevation Distribution Methods.
  2. a) The term “NC” (normal crown) represents an equal downward cross-slope, typically 2%, on each side of the axis of rotation.
    b) The minimum curve radii for normal crown are suitable up to 3.0%.
    c) 3.0% normal crown should only be used when 3 or more lanes are sloped in the same direction.
    d) 1.5% or flatter normal crown should only be used for the design of special circumstance, such as table-topping intersections, or the evaluation of existing conditions
  3. The term “RC” (reverse crown) represents a curve where the downward, or adverse, cross-slope should be removed by superelevating the entire roadway at the normal cross-slope rate
  4. . For curve radii falling between normal crown and reverse crown, rather than interpolation a superelevation rate equal to the normal crown should typically be used.
  5. Low-Speed values are shown for use on Rural Facilities with low operating speeds. These values are also provided for design exception documentation on High-Speed facilities.
Table 4-7: Minimum Radii and Superelevation Rates
1
 for Rural and High-Speed Suburban, Urban and Urban Core Facilities, e
max
 = 8%
Design Speed
e
(%)
15
mph
R (ft)
20
mph
R (ft)
25
mph
R (ft)
30
mph
R (ft)
35
mph
R (ft)
40
mph
R (ft)
45
mph
R (ft)
50
mph
R (ft)
55
mph
R (ft)
60
mph
R (ft)
65
mph
R (ft)
70
mph
R (ft)
75
mph
R (ft)
80
mph
R (ft)
NC
2,4
932
1,640
2,370
3,240
4,260
5,410
6,710
8,150
9,720
11,500
12,900
14,500
16,100
17,800
RC
3,4
676
1,190
1,720
2,370
3,120
3,970
4,930
5,990
7,150
8,440
9,510
10,700
12,000
13,300
2.2
605
1,070
1,550
2,130
2,800
3,570
4,440
5,400
6,450
7,620
8,600
9,660
10,800
12,000
2.4
546
959
1,400
1,930
2,540
3,240
4,030
4,910
5,870
6,930
7,830
8,810
9,850
11,000
2.6
496
872
1,280
1,760
2,320
2,960
3,690
4,490
5,370
6,350
7,180
8,090
9,050
10,100
2.8
453
796
1,170
1,610
2,130
2,720
3,390
4,130
4,950
5,850
6,630
7,470
8,370
9,340
3.0
415
730
1,070
1,480
1,960
2,510
3,130
3,820
4,580
5,420
6,140
6,930
7,780
8,700
3.2
382
672
985
1,370
1,820
2,330
2,900
3,550
4,250
5,040
5,720
6,460
7,260
8,130
3.4
352
620
911
1,270
1,690
2,170
2,700
3,300
3,970
4,700
5,350
6,050
6,800
7,620
3.6
324
572
845
1,180
1,570
2,020
2,520
3,090
3,710
4,400
5,010
5,680
6,400
7,180
3.8
300
530
784
1,100
1,470
1,890
2,360
2,890
3,480
4,140
4,710
5,350
6,030
6,780
4.0
277
490
729
1,030
1,370
1,770
2,220
2,720
3,270
3,890
4,450
5,050
5,710
6,420
4.2
255
453
678
955
1,280
1,660
2,080
2,560
3,080
3,670
4,200
4,780
5,410
6,090
4.4
235
418
630
893
1,200
1,560
1,960
2,410
2,910
3,470
3,980
4,540
5,140
5,800
4.6
215
384
585
834
1,130
1,470
1,850
2,280
2,750
3,290
3,770
4,310
4,890
5,530
4.8
193
349
542
779
1,060
1,390
1,750
2,160
2,610
3,120
3,590
4,100
4,670
5,280
5.0
172
314
499
727
991
1,310
1,650
2,040
2,470
2,960
3,410
3,910
4,460
5,050
5.2
154
284
457
676
929
1,230
1,560
1,930
2,350
2,820
3,250
3,740
4,260
4,840
5.4
139
258
420
627
870
1,160
1,480
1,830
2,230
2,680
3,110
3,570
4,090
4,640
5.6
126
236
387
582
813
1,090
1,390
1,740
2,120
2,550
2,970
3,420
3,920
4,460
5.8
115
216
358
542
761
1,030
1,320
1,650
2,010
2,430
2,840
3,280
3,760
4,290
6.0
105
199
332
506
713
965
1,250
1,560
1,920
2,320
2,710
3,150
3,620
4,140
6.2
97
184
308
472
669
909
1,180
1,480
1,820
2,210
2,600
3,020
3,480
3,990
6.4
89
170
287
442
628
857
1,110
1,400
1,730
2,110
2,490
2,910
3,360
3,850
6.6
82
157
267
413
590
808
1,050
1,330
1,650
2,010
2,380
2,790
3,240
3,720
6.8
76
146
248
386
553
761
990
1,260
1,560
1,910
2,280
2,690
3,120
3,600
7.0
70
135
231
360
518
716
933
1,190
1,480
1,820
2,180
2,580
3,010
3,480
7.2
64
125
214
336
485
672
878
1,120
1,400
1,720
2,070
2,470
2,900
3,370
7.4
59
115
198
312
451
628
822
1,060
1,320
1,630
1,970
2,350
2,780
3,250
7.6
54
105
182
287
417
583
765
980
1,230
1,530
1,850
2,230
2,650
3,120
7.8
48
94
164
261
380
533
701
901
1,140
1,410
1,720
2,090
2,500
2,970
8.0
38
76
134
214
314
444
587
758
960
1200
1,480
1,810
2,210
2,670
Notes:
  1. . Computed using Superelevation Distribution Method 5. See AASHTO’s A Policy on Geometric Design of Highways and Streets for the different types of Superelevation Distribution Methods.
  2. a) The term “NC” (normal crown) represents an equal downward cross-slope, typically 2%, on each side of the axis of rotation.
    b) The minimum curve radii for normal crown are suitable up to 3.0%.
    c) 3.0% normal crown should only be used when 3 or more lanes are sloped in the same direction.
    d) 1.5% or flatter normal crown should only be used for the design of special circumstance, such as table-topping intersections, or the evaluation of existing conditions
  3. The term “RC” (reverse crown) represents a curve where the downward, or adverse, cross-slope should be removed by super elevating the entire roadway at the normal cross-slope rate.
  4. For curve radii falling between normal crown and reverse crown, rather than interpolation a superelevation rate equal to the normal crown should typically be used.