Anchor: #i1026076

## Section 4: Ramps and Direct Connections

Anchor: #i1026081

### Overview

Ramps and direct connections are designed to the same criteria.

This subsection discusses ramps and direct connections and includes information on the following topics:

Anchor: #i1026126

### Design Speed

Similar to facilities with design speeds of 80 mph [130 km/h] or less, ramps on these facilities should also have a relationship between the ramp design speed and the mainlane design speed. The current relationship, in general, is for the ramp design speed to be 85 or 70 percent of the highway design speed, rounded up to the nearest 5 mph [10 km/h] increment, and limiting the speed differential to 10 mph [20 km/h] on the upper range and 20 mph [30 km/h] for the mid-range.

Table 8-12 shows the values for ramp/connector design speeds.

Anchor: #i1018261Table 8-12: Guide Values for Ramp/Connection Design Speed as Related to Highway Design Speed1

(US Customary)

Ramp Design Speed (mph):

Highway Design Speed (mph)

85

90

95

100

Upper Range (85%)

75

80

85

90

Mid-Range (70%)

65

70

75

80

(Metric)

Ramp Design Speed (km/h)

Highway Design Speed (km/h)

140

150

160

Upper Range (85%)

120

130

140

Mid-Range (70%)

110

120

130

1 Values determined by calculating the 85 or 70% value of the highway design speed and rounding up to the nearest 5 mph [10 km/h] increment and then adjusting if the rounded value is more than the cap amount from the highway design speed (10 mph [20 km/h] for upper range and 20 mph [30 km/h]for mid range).

Anchor: #i1026140

### Lane and Shoulder Widths

Ramp and Direct Connection shoulder widths (inside and outside) and lane widths are shown in Table 8-13.

Anchor: #i1018369Table 8-13: Ramp and Direct Connection Widths

(US Customary)

Inside Shoulder Width (ft)

Outside Shoulder Width1 (ft)

Traffic Lanes (ft)

1-lane

8

10

14

2-lane

4

10

26

(Metric)

Inside Shoulder Width (m)

Outside Shoulder Width1 (m)

Traffic Lanes (m)

1-lane

2.4

3.0

4.3

2-lane

1.2

3.0

7.9

1If sight distance restrictions are present due to horizontal curvature, the shoulder width on the inside of the curve may be increased to 10 ft [3.0 m] and the shoulder width on the outside of the curve decreased to 8 ft [2.4 m] (one lane) or 4 ft [1.2 m] (two lane).

Anchor: #i1026149

### Acceleration and Deceleration Lengths

Table 8-14 provides design criteria for exit ramp deceleration and taper lengths. Adjustment factors for grade effects are independent of highway design speed, therefore use Table 3-14 for deceleration length adjustment factors.

Table 8-15 provides design criteria for entrance ramp acceleration and taper lengths; adjustment factors for grade effects are shown in Table 8-16.

 Highway Design Speed (mph) Minimum Length of Taper, T (ft) Deceleration Length, D (ft) for Exit Curve Design Speed (mph) Stop 15 20 25 30 35 40 45 50 55 60 65 70 75 Assumed Exit Curve Speed (mph) 0 14 18 22 26 30 36 40 44 48 52 55 58 61 30 35 40 45 50 55 60 65 70 75 Existing Criteria in Roadway Design Manual Figure 3-36 -- -- -- -- -- -- 185 225 270 310 -- -- -- -- -- -- -- 185 225 265 -- -- -- -- -- -- -- -- 190 235 -- -- -- -- -- -- -- -- -- 195 -- -- -- -- -- -- -- -- -- -- 80 335 310 275 240 200 85 90 95 100 345 360 370 425 650 695 780 900 630 675 760 880 615 660 745 865 595 645 725 850 575 625 705 830 550 600 680 805 510 555 640 760 475 525 605 730 440 490 570 695 355 400 450 530 655 310 355 405 485 610 275 325 370 455 575 240 285 335 415 540 200 250 295 375 500 NOTE: Where providing desirable deceleration length is impractical, it is acceptable to allow for a moderate amount of deceleration (10 mph) within the through lanes and to consider the taper as part of the deceleration length.

 Highway Design Speed (km/h) Minimum Length of Taper, T (m) Deceleration Length, D (m) for Exit Curve Design Speed (km/h) Stop 20 30 40 50 60 70 80 90 100 110 120 Assumed Exit Curve Speed (km/h) 0 20 28 35 42 51 63 70 77 85 91 98 50 60 70 80 90 100 110 120 Existing Criteria in Roadway Design Manual Figure 3-36 -- -- -- -- -- 56 78 102 -- -- -- -- -- -- 52 78 -- -- -- -- -- -- -- 58 -- -- -- -- -- -- -- -- 130 116 92 73 -- 140 150 160 110 115 130 248 271 309 241 264 303 234 258 297 226 250 290 217 241 282 202 227 268 178 204 248 162 189 233 144 172 216 121 150 196 103 132 180 80 110 159 NOTE: Where providing desirable deceleration length is impractical, it is acceptable to allow for a moderate amount of deceleration (15 km/h) within the through lanes and to consider the taper as part of the deceleration length.

 Highway Design Speed (mph) Minimum Length of Taper, T (ft) Acceleration Length, A (ft) for Entrance Curve Design Speed (mph) Stop 15 20 25 30 35 40 45 50 55 60 65 70 75 Initial Speed (mph) 0 14 18 22 26 30 36 40 44 48 52 55 58 30 35 40 45 50 55 60 65 70 75 Existing Criteria in Roadway Design Manual Figure 3-36 -- -- -- -- -- -- -- 132 331 545 -- -- -- -- -- -- -- -- 70 287 -- -- -- -- -- -- -- -- -- 74 -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 80 771 516 306 79 -- 85 90 95 100 345 360 370 425 2186 2403 2786 3372 2154 2379 2777 3385 2045 2266 2658 3256 2006 2233 2636 3250 1945 2179 2593 3225 1828 2065 2484 3123 1601 1840 2264 2910 1426 1668 2097 2751 1227 1472 1906 2568 1009 1259 1701 2375 757 1010 1459 2142 550 805 1258 1949 326 584 1042 1740 84 345 808 1514 NOTE: Uniform 50:1 to 70:1 tapers are recommended where lengths of acceleration lanes exceed 1,300 ft.

 Highway Design Speed (km/h) Minimum Length of Taper, T (m) Acceleration Length, A (m) for Entrance Curve Design Speed (km/h) Stop 20 30 40 50 60 70 80 90 100 110 120 Initial Speed (km/h) 0 20 30 40 47 55 63 70 77 85 91 98 50 60 70 80 90 100 110 120 Existing Criteria in Roadway Design Manual Figure 3-36 -- -- -- -- -- -- 48 156 -- -- -- -- -- -- -- 46 -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 130 218 109 -- -- 140 150 160 110 115 130 703 819 977 687 806 987 793 945 652 776 940 624 750 928 572 700 877 507 646 787 438 581 726 350 492 657 245 392 570 155 305 496 37 190 397 Note: Uniform 50:1 to 70:1 tapers are recommended where lengths of acceleration lanes exceed 400 m.

Anchor: #i1026163

### Distance between Successive Ramps

The minimum acceptable distance between ramps is dependent upon the merge, diverge, and weaving operations that take place between ramps and the Highway Capacity Manual should be used for analysis of these requirements. Several iterations of the analysis may be required to determine these lengths at the higher design speeds. The distances required for adequate signing should also be considered.

Anchor: #i1026173