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Section 4: Two-Lane Rural Highways

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Overview

The general geometric features for two-lane rural highways are provided in this section and are summarized in the following tables and figures:

  • Figure 3-5: Typical cross section
  • Table 3-6: Minimum Design Speed for Rural Two-lane Highways : Minimum design speed
  • Table 3-7. Geometric Design Criteria for Rural Two-Lane Highways : Basic design criteria and cross sectional elements
  • Table 3-8: Width of Travel Lanes and Shoulders on Rural Two-lane Highways : Lane and shoulder widths
  • Table 3-9: Minimum Structure Widths For Bridges to Remain in Place on Rural Two-lane Highways : Minimum structure widths that may remain in place.

    Additional information on structure widths may be obtained in the Bridge Design Manual and the Bridge Project Development Manual.

    Anchor: #CIHBDAJFTable 3-6: Minimum Design Speed for Rural Two-lane Highways

    (US Customary)

    Functional

    -

    Minimum Design Speed (mph) for future ADT of:

    Class

    Terrain

    < 400

    400-1500

    1500-2000

    > 2000

    Arterial

    Level

    Rolling

    70

    60

    Collector

    Level

    Rolling

    501

    402

    50

    40

    50

    40

    60

    50

    Local3

    Level

    Rolling

    402

    30

    50

    40

    50

    40

    50

    40

    (Metric)

    Functional

    -

    Minimum Design Speed (km/h) for future ADT of:

    Class

    Terrain

    < 400

    400-1500

    1500-2000

    > 2000

    Arterial

    Level

    Rolling

    110

    100

    Collector

    Level

    Rolling

    801

    602

    80

    60

    80

    60

    100

    80

    Local3

    Level

    Rolling

    602

    50

    80

    60

    80

    60

    80

    60

    1 A 40 mph [60 km/h] minimum design speed may be used where roadside environment or unusual design considerations dictate.

    2 A 30 mph [50 km/h] minimum design speed may be used where roadside environment or unusual design considerations dictate.

    3 Applicable only to off-system routes that are not functionally classified at a higher classification.



    Anchor: #CIHEEIEITable 3-7. Geometric Design Criteria for Rural Two-Lane Highways

    (US Customary)

    Geometric Design Element

    Functional Class

    Reference or Design Value

    Design Speed

    All

    Table 3-6

    Minimum Horizontal Radius

    All

    Table 2-3and Table 2-4

    Max. Gradient

    All

    Table 2-9

    Stopping Sight Distance

    All

    Table 2-1

    Width of Travel Lanes

    All

    Table 3-8

    Width of Shoulders

    All

    Table 3-8

    Vertical Clearance, New Structures

    All

    16.5 ft1

    Horizontal Clearance

    All

    Table 2-11

    Pavement Cross Slope

    All

    Chapter 2, Pavement Cross Slope

    (Metric)

    Geometric Design Element

    Functional Class

    Reference or Design Value

    Design Speed

    All

    Table 3-6

    Minimum Horizontal Radius

    All

    Table 2-3and Table 2-4

    Max. Gradient

    All

    Table 2-9

    Stopping Sight Distance

    All

    Table 2-1

    Width of Travel Lanes

    All

    Table 3-8

    Width of Shoulders

    All

    Table 3-8

    Vertical Clearance, New Structures

    All

    5.0 m1

    Horizontal Clearance

    All

    Table 2-11

    Pavement Cross Slope

    All

    Chapter 2, Pavement Cross Slope

    1 Exceptional cases near as practical to 16.5 ft [5.0 m] but never less than 14.5 ft [4.4 m].



    Anchor: #CIHHGBFFTable 3-8: Width of Travel Lanes and Shoulders on Rural Two-lane Highways

    (US Customary)

    Functional Class

    Design Speed (mph)

    Minimum Width 1,2(ft) for future ADT of:

    -

    -

    < 400

    400-1500

    1500-2000

    > 2000

    Arterial

    LANES (ft)

    -

    All

    12

    -

    SHOULDERS (ft)

    -

    All

    43

    43 or 83

    83

    8 - 103

    Collector

    LANES (ft)

    -

    30

    10

    10

    11

    12

    -

    35

    10

    10

    11

    12

    -

    40

    10

    10

    11

    12

    -

    45

    10

    10

    11

    12

    -

    50

    10

    10

    12