Appendix_E_-_roadclassificationrev.pdf

Appendix E Functional Classification and Design Criteria Analysis

S:\Tranproj\100013881\Admin\Memorandums\Design Tech Memo\roadclassificationrev.doc

Technical Memorandum Beartooth Highway WY FS 4-1(4)

Date: March 28, 2003 From: PBS&J To: FHWA Subject: Beartooth Highway Functional Classification and Design Criteria Analysis Rural Minor Arterial vs. Special-Purpose Recreation Road

Introduction This technical memorandum addresses the selection of the functional classification for Segment 4 of the Beartooth Highway (Highway). The first step in the transportation planning process is to determine the functional classification of the roadway. Functional classifications group streets and highways according to the character of service they are intended to provide. This analysis was completed to compare rural minor arterial and special-purpose recreation road (subcategory of rural local roads) design criteria.

Definitions Rural Minor Arterial The rural minor arterial system has the following characteristics:

1. Linkage of cities, larger towns, and other traffic generators (such as major resort areas) that are capable of attracting travel over similarly long distances.

2. Integrated interstate and intercounty service.

3. Internal spacing consistent with population density, so that all developed areas of the state are within reasonable distance of arterial highways.

4. Corridor movements consistent with items (1) and (3) with trip lengths and travel densities greater than those predominantly served by rural collector or local systems.

Local Roads A local road or street serves primarily to provide access to farms, residences, businesses, or other abutting properties. Even though the predominant function of local roads is providing access to adjacent property, some local roads and streets serve a limited amount of through traffic. Such roads include design criteria and traffic control features more typical of collectors and arterials for safety purposes. On these roads the through traffic is local in nature rather than regional, intrastate, or interstate.

Special-Purpose Recreation Roads Special-purpose roads are local roads but are classified differently because of their unique character. Special-purpose roads include recreational roads, resource recovery roads, and local service roads. The roads in this category are lightly traveled and operate with low traffic speeds. Special-purpose roads are intended to protect and enhance the existing aesthetic, ecological, environmental, and cultural amenities distinguishing the recreational site or area.

A recreation road in this category is a road serving recreational sites and areas and the road is part of the recreational experience. Visitors to a specific recreational site need access to the general area, usually by a statewide or principal arterial highway. Second, they need access to the specific recreational site, which is the recreation road classification. Recreational roads can be identified as primary access roads, circulation roads, and area roads in the recreation site. Primary access roads are defined as roads that allow through movement into and between access areas. Circulation roads allow movement between activity sites within an access area, whereas area roads allow direct access to individual activity areas, such as campgrounds, park areas, boat launching ramps, picnic groves, and scenic and historic sites. These types of roads are often one-way or two-way single lane roads.

Selection of Functional Classification for the Beartooth Highway The functional classification for the entire Highway has been selected as rural minor arterial based on the characteristics of the Highway and the Origin-Destination Survey.

The findings of the O-D survey indicated that a high percentage of users were using to the highway to travel between towns and to access the Park. This use is consistent with the original intent of the construction of the roadway, which was to provide access to the Yellowstone National Park. The Highway is located within a rural area. In addition, the Highway primarily serves regional travel between Red Lodge, Montana and Yellowstone National Park, consistent with an arterial classification. The Highway also serves a secondary function of providing access to adjacent recreation sites and areas, which is consistent with a collector classification. However, this is not a sufficient reason to classify the Highway as a special-purpose recreational road. The primary purpose for the Highway is to provide a link between towns, which is not the function of a special-purpose road. Furthermore, the projected SADT for the Highway by the year 2025 is 1,972 vehicles, which is far greater than the generally light traffic volumes typically found on special-purpose recreation roads. For these reasons, the entire Highway is classified as a rural minor arterial.

Additional consideration must be given to the fact that the segments of the Highway in Montana (segment 1) and the other segments in Wyoming (segments 2 and 3) have been reconstructed or are proposed for reconstruction using design criteria for rural minor arterial. Additionally, the Montana Department of Transportation has classified all segments in Montana (segments 1, 5, 6, and 7) as a rural minor arterial. Segment 4 was originally constructed as a rural minor arterial and should have similar design criteria based on driver expectancy between adjacent segments.

With respect to the dual function of the Highway (e.g. it acts as a through route as well as providing access to adjacent recreational facilities) this dual nature can be addressed within the range of design standards permitted by the rural minor arterial classification.

The implementation of design standards combined with the incorporation of context sensitive design techniques serve to minimize the impacts to the existing aesthetic, ecological, environmental, and cultural amenities distinguishing the Highway.

Design Criteria The design criteria for both rural minor arterials and special purpose roads are detailed below in a comparison table. Both the FHWA and the Wyoming Department of Transportation have adopted AASHTO guidelines for design criteria. The design criteria including stopping sight distance, passing sight distance, vertical alignment, and horizontal alignment are selected based on design speed. Differences between a minor rural arterial and a special-purpose recreation road are minimal. Furthermore, these differences are reduced by the lower design speeds selected for the Beartooth Highway.

AASHTO Design Criteria

Proposed Design Criteria

Segment 4-Beartooth Hwy

AASHTO Criteria AASHTO Criteria

Rural Minor Arterial Special-Purpose Recreation Road (Primary Access)

Design Speed 50 – 60 km/hr (31 – 37 mph)

60 - 80 km/hr (40 - 50 mph) mountainous 60 km/hr (40 mph)

Design Vehicle BUS-12 (40 ft.) BUS-12 (40 ft.) Motor home, vehicle w/ trailer, car

Stopping Sight Distance

65 m (50 km/hr); 85 m (60 km/hr) 85 m (60 km/hr) 85 m (60 km/hr)

Passing Sight Distance

345 m (50 km/hr); 410 m (60 km/hr) 410 m (60 km/hr) 410 m (60 km/hr)

Maximum Grade 8 % 8 % mountainous 12 % mountainous

Vertical Alignment4 Kcrest = 7, Ksag = 13 (50 km/hr); Kcrest = 11, Ksag = 18 (60 km/hr)

Kcrest = 11, Ksag = 18 (60 km/hr)

Kcrest = 11, Ksag = 18 (60 km/hr)

Horizontal Alignment

Min. Radius = 90 m (50 km/hr); 135 m (60 km/hr)

Minimum Radius = 125 m (60 km/hr) (8% Superelevation)

Minimum Radius = 135 m (60 km/hr)

Superelevation Maximum 6 % Maximum 8% Maximum 6%

Travel Lane Width 7.2 m (24 ft.) 6.6 m (22 ft.) 6.6 – 7.2 m (22 - 24 ft.)

Shoulder Width 0.6 – 0.9 m (2 - 3 ft.) 1.8 m (6 ft.) 0.6 – 1.2 m (2 – 4 ft.)

Curve Widening3 Yes Yes Yes

Cross Slope 2 % 1.5 to 2 % 1.5 to 2 % Guardrail Offset 0.6 m (2 ft.)+shoulder 1.4 m (4.6 ft.) 0.6 m (2 ft.)+shoulder

Clear Zone1 3 m (10 ft.) 3.5 – 4.5 m (11.5 – 15 ft.) based on slopes 3 m (10 ft.)

Foreslope2 2.4 m fixed width 1:5 or flatter 1:4 or flatter Vertical Clearance 4.9 m (16 ft.) 4.9 m (16 ft.) 4.3 m (14 ft.)

Structure Offset 0.6 m (2 ft.) each side 1.2 m (4 ft.) each side 1 m (3 ft.)

Structure Loading MS-18 (HS-20) MS-18 (HS-20) M 13.5 (H15) Notes:

1. Federal Lands Highway Project Development and Design Manual states that the clear zone width should be a minimum of 3.0 m.

2. WYDOT Road Design Manual states that for reconstruction, foreslopes should be a minimum of 1:8 or flatter.

3. AASHTO state that widening is needed on certain curves because the design vehicle occupies a greater width because the rear wheels track inside front wheels on curves and drivers experience difficulty in steering their vehicles in the center of the lane. Widening on the inside of curves should be provided; additional width equal to 35 divided by the curve radius in meters is recommended for special-purpose recreation roads.

Widening on the inside of simple curves and equally on both sides of spiral curves should be provided;

additional width can be determined by using the track width, lateral clearance, front overhang, and wheelbase of the design vehicle, width allowance for difficulty of driving on curves, and the curve radius for minor rural arterials. A table with values for curve widening based on design vehicles, roadway width, and curves radius is used for reference in AASHTO with adjustment factors for the design vehicles.

4. The rate of vertical curvature, K, is the length of curve per percent algebraic difference in intersecting grades.