4.0 Minor Arterial Roads and Streets

Basic Geometric Standards
Level of Service
Design Speed
Sight Distance
.....Stopping Sight Distance
.....Corner Sight Distance
Lane and Shoulder Widths for Urban And Village Minor Arterials
Lane and Shoulder Widths on Rural Minor Arterials
Bridge Widths and Structural Capacities
Vertical Clearance
Horizontal Clearance
Alignment
Grades
Cross-slope
Superelevation
Bicycle and Pedestrian Considerations
........Shared Use of the Highway by Bicycles
........Bicycles on Bridges
........Designated Bicycle Routes and Lanes
........Pedestrian Facilities
Special Design Guidelines
........Common Tools
........Historic/Archaeological Considerations
........Natural Resources
........Recreational Resources
........Scenic Roads or Views Considerations
........Village or City Entrance Considerations
........Economic Vitality Considerations

4.1 Basic Geometric Standards  (Back to top of page)

4.2 Level of Service  (Back to top of page)

4.3 Design Speed  (Back to top of page)

> To avoid and/or minimize impacts to historical, architectural, scenic, natural or other resources.

           > To avoid excessive costs of construction.

> To better comply with a town or regional plan.

4.4 Sight Distance  (Back to top of page)

4.4.1  Stopping Sight Distance  (Back to top of page)

Minimum stopping sight distances on rural and urban Minor Arterials will adhere to the values in Table 4.1.

Corner sight distances for rural and urban minor arterials will meet the minimum requirements of Table 4.2.

4.5 Lane and Shoulder Widths for Urban And Village Minor Arterials
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Due to the large variations in urban and village settings, no table of values has been given, however, the following guidelines will apply. On urban and village Minor Arterials, lane widths may vary from 10 to 12 feet, and there should be appropriate offsets to curb. The 10-foot widths are appropriate in highly restricted areas having little or no truck traffic. The 11-foot lanes are used extensively for urban and village Minor Arterial street designs. The 12-foot lane widths are generally used on all higher speed, free-flowing principal Minor Arterials. Under interrupted-flow conditions at low speeds up to 45 mph, the narrower lane widths are normally adequate and have some advantages. Reduced lane widths allow a greater number of lanes in restricted right-of-way areas and facilitate pedestrian crossings because of reduced distance. They are also more economical to construct. An 11-foot lane width is adequate for through lanes, continuous two-way left-turn lanes and a lane adjacent to a painted median. A 10-foot left-turn lane, or a combination lane used for parking, with traffic during peak hours, is also acceptable.

Lane and shoulder widths within historic districts should be compatible with the historic character of the district.

Shoulders are desirable on urban and village Minor Arterials, and should be provided where feasible to facilitate maneuvering, space for immobilized vehicles, safety for the pedestrian in areas where sidewalks are not provided, safe accommodation of bicycles, speed-change lanes for vehicles turning into driveways, and storage space for plowed snow. Despite these advantages, the width of shoulders in urban and village areas may be restricted because of available right-of-way, adjacent development and other constraints.

Where shoulders are provided to accommodate disabled vehicles, they must be at least 6 feet wide. Parking lanes require approximately 7 feet of actual street space. The desirable minimum width is 8 feet, however, to provide better clearance and the potential to use the parking lane as a travel lane during peak periods a parking lane width of 10 to 12 feet is desirable.

As an absolute minimum, where no bicycles are to be accommodated, a 2-foot offset to vertical curb should be provided, and a 1-foot offset to sloped curb. In all cases, drainage grates and drop inlets should be designed so that they do not project into a travel lane. Drainage grates should always be bicycle-safe in design.

Lane and shoulder widths on rural Minor Arterials will adhere to values in Table 4.3. Note that the shoulder widths in this table are considered necessary for adequate safety and service for this class of highway, and may exceed the minimum paved widths needed solely to provide bicycle safety. The required shoulder width beyond that needed to adequately accommodate bicycles as defined in Section 4.14 need not be paved.

Lane and shoulder widths within historic districts should be compatible with the historic character of the district.

State policy favors the rehabilitation of existing bridges. In choosing between the rehabilitation of an existing bridge and the construction of a new bridge, whether on the existing location or on a new location, the agency shall weigh the following factors:

1. the functional classification of the highway;

2. the load capacity and geometric constraints of the bridge and the availability of alternative routes;

3. the comparative long-term costs, risks, and benefits of rehabilitation and new construction;

4. the requirements of state standards for geometric design;

5. disruption to homes and businesses;

6. environmental impacts;

7. the potential effects of the local and state economies;

8. cost-effectiveness;

9. mobility, including bicycles and pedestrians;

10. safety, as determined by factors such as accident history for motorists, pedestrians, and bicyclists;

11. local or regional plans as interpreted by the adopting entity, and state agency plans;

12. the impact on the historic, scenic, and aesthetic values of the municipality, as interpreted by the municipality, in which the highway is located; and

13. if it is a forest highway under federal jurisdiction.

State policy for the reconstruction of bridges on Minor Arterials favors preservation within existing footprints, in order to ensure compatibility with the Vermont setting and to reduce costs and environmental impacts. Where reconstruction within the existing footprint is not feasible, the full width of approach roadways as shown in Table 4.3 should be provided across all new bridges on rural Minor Arterials, and the same curb-to-curb width as the street across all new and replacement bridges on urban and village Minor Arterials. New bridges should be designed to HS-25 loading capacity.

With regard to a bridge located on a municipal highway, a municipality may request the agency to adhere to one or more of the following guidelines:

1. where feasible, the rehabilitated or replacement bridge shall occupy the same curb-to-curb width or alignment, or both, as the existing bridge or the existing approaches to the existing bridge, or both;

2. unless otherwise required by law, a bridge that does not already carry a sidewalk may be rehabilitated without adding a sidewalk and a replacement bridge may be built without a sidewalk or with a sidewalk on only one side; or

3. in rehabilitating a historically significant bridge, the design of the rehabilitated bridge must retain the bridge’s historic character, to the extent feasible.

Historic bridges in urban, village, or rural historic districts or those in scenic corridors should be considered for design exceptions so that they may remain in place on minor arterials and be considered for future rehabilitation rather than replacement.

New or reconstructed structures should provide at least 14 feet of vertical clearance over the entire roadway width, including shoulders plus and additional clearance of 3 inches for future resurfacing of the under passing road.

Structures over railroads should provide a minimum vertical clearance of 23 feet over both rails, unless otherwise provided in a variance agreement entered into by the VAOT, the railroad and any affected municipality, and approved by the Transportation Board in accordance with 5 VSA, Section 3670. Where "double-stacks" are to be accommodated on the railroad, an absolute minimum vertical clearance of 20.75 feet will be required.

Bridges over rivers and other bodies of water will, where practicable, be designed to pass the 50-year frequency flood with a minimum clearance of 1 foot between the water surface elevation and the low chord of the bridge. In addition, overtopping of the road should not be permitted during the 50-year flood. Consideration shall also be given to the potential effects of the 100-year flood on upstream and downstream property, the environment, hazards to human life and floodplain management criteria.

A clear unobstructed roadside is highly desirable for motorist safety along rural minor arterials. Clear zone distances for new construction and reconstruction projects on rural minor arterials will normally be based on the values shown in Table 4.4.

Despite the recommendations of Table 4.4, clear zones as narrow as 10 feet may be used on rural minor arterials, without design exception, where necessary to avoid or minimize disturbance of significant historic, archaeological, scenic, natural or other resources. In addition, on low speed (45 mph or less) rural minor arterials, clear zones may be limited to 10 feet, irrespective of the recommendations of Table 4.4.

On uncurbed urban and village minor arterials, clear zones will be the same as for rural areas.

On curbed minor arterial urban and village streets, a 1.5 foot horizontal offset to obstructions from face of curb should be provided. This dimension should be increased to 3 feet near turning radii at intersections with side roads and driveways.

Horizontal curvature will normally be designed in accordance with recommended AASHTO values for the design speed. However, curves up to 10 mph below the stated design speed may be used, without design exception, where necessary to avoid and/or minimize disturbance of historic, archaeological, scenic, natural or other resources. In addition, horizontal curves within 750 feet of a stop sign may be designed up to 15 mph below the stated design speed without design exception. When curvature sharper than the AASHTO recommended values is used, a post-construction test of those curves will be conducted, and advisory speeds will be posted where appropriate.

Maximum grades on rural and urban Minor Arterials will adhere to the values shown in Tables 4.5 and 4.6. In curbed areas of village and urban streets and on all bridges, grades less than 1 percent should be avoided where possible to promote efficient runoff of storm water.

Two-lane pavements are normally designed with a centerline crown and a parabolic surface with an average cross slope of 2 percent. When drainage is carried across adjacent lanes, the cross slope may be increased from one lane to another. Refer to the VAOT design manual for cross-slope design in various situations.

When the use of curves is required on a rural Minor Arterial alignment, a superelevation rate compatible with the design speed must be used. Superelevation of curves on rural Minor Arterials should not exceed 8 percent. Where a side road intersects on the outside of a main road curve, superelevation of the main road curve should be limited to 6 percent or less to prevent operational difficulties for vehicles entering the main road under snowy or icy conditions.

Superelevation is generally not used on low-speed (45 mph or less) curbed urban and village streets. This is to avoid problems with such items as drainage, ice formation, driveways, pedestrian crossings and developed property. Refer to the 1990 AASHTO Policy, Chapter III, for a detailed discussion of design for low-speed urban streets.

Bicycles and pedestrian traffic may be expected along the sides of most Minor Arterial roads and streets, except those which are designed and posted as limited access facilities. Where bicycles and pedestrians are allowed by law, the roadway should be designed and constructed under the assumption that it will be used by bicyclists and pedestrians. Bicycles require a paved surface; pedestrians, however, may often be adequately accommodated on unpaved roadway shoulders.

In recent decades, highways were not always designed with bicycle and pedestrian travel in mind. There are many ways in which roadway corridors should be improved to more safely accommodate bicycle and pedestrian traffic. Bicycle accommodation within the highway corridor may take four forms: (1) shared use of the highway by bicycles and motor vehicles, (2) designated bicycle route, (3) designated bicycle lane, or (4) a separated bicycle path. Many of the tools listed in section 4.15.1 provide roadways which are safer for bicyclists and pedestrians.

Adequate accommodation of bicycles in rural areas is usually provided by paved shoulders designed to the widths shown in section 4.6 above. However, where shoulder width is less than those values, where shoulder paving must be minimized and in urban or village areas, Tables 4.7, 4.8 and 4.9 provide additional guidance in the selection of appropriate widths of paved areas to safely accommodate bicycles and motor vehicles on the same facility. Note that additional width may be desirable in very high traffic areas or where sight distance is restricted.

In lieu of a paved shoulder, it is permissible to use a shared-use curb lane of at least the width shown in Table 4.9. When a shared-use lane is employed, a white edge line should be placed within 1 foot of the face of curb to discourage parking. For all shared-use curb lanes, recessed drainage inlets or curb inlets should be used.

Wherever bicycles are to be accommodated on newly constructed bridges, shoulders and paved areas with a minimum dimension as shown in Tables 4.7, 4.8 and 4.9 should be provided between the parapet, rail or barrier and the edge of the nearest travel lane.

Designated bicycle routes or lanes may be appropriate along some Minor Arterial highways. Because designated routes and lanes will attract bicyclists encompassing a wide range of abilities, special care must be taken to ensure adequate width. Principal concerns for designated bicycle routes and lanes are rider safety and comfort. Because of these concerns, some high speed and/or high volume arterial routes may not be appropriate for designated routes and lanes. In such cases, alternate routes or separate paths for bicycles may be desirable.

Adequate accommodation of pedestrians must be designed for all roadway projects. Depending on the locality and expected frequency of pedestrians, adequate accommodation may range from a graded space alongside a rural road to a sidewalk in a village or city. Projects in urban or village areas shall include consideration of sidewalks and crossing locations. In addition, at the request of a municipality, sidewalks should be considered in other areas of expected pedestrian use such as near schools and recreation areas.

Where pedestrians are accommodated on sidewalks, the design must observe, to the extent possible, current Americans with Disabilities Act Accessibility Guidelines (ADAAG). These guidelines establish acceptable grades, cross-slopes, widths, ramps, surface textures and other facets of pedestrian facility design.

Pedestrian accommodation on combined bicycle/pedestrian paths must also respect the ADAAG to the extent feasible.

Pedestrian accommodation along the shoulders of roadways do not need to comply with ADAAG. However, to the extent that those guidelines can reasonably be achieved, the designer is urged to do so.

These Special Design Guidelines are presented to assist the designer in avoiding, minimizing, or mitigating negative impacts upon the environment and other sensitive resources as well as to enhance the design to fit the context of the project site. These Special Design Guidelines note the importance of the individual resources and suggest tools which may be used in the development of a design which recognizes the resource at the proper level of importance. Under this Functional Classification there are guidelines for:

> Scenic Resources

> Village or City Entrance Considerations

> Economic Vitality Considerations

When such resources are present within a project site and the use of the tools suggested do not provide an adequate protection of the resources then the design may be eligible for reductions in geometric values. The decision to pursue reductions in the standards is subject to approval in accordance with the "VAOT Design Exception Policy".

The primary strategy for Minor Arterial projects on new alignment should be to use alternative roadway alignments to avoid the impact on the resource. When the project must remain on existing alignment such as a major roadway reconstruction, "Preservation" or "3R" project, bridge repair or replacement, design solutions should be pursued that minimize the extent of the impact. Reduction in the size/area of impact, and the utilization of creative design and engineering solutions should be pursued. Major tools to be used include the alteration of the proposed cross section and the reduction of design speed within sensitive resource areas. Other strategies are described as "common tools" in the following subsection.

> Reduction in posted speed

> Reduction/minimization of lane and shoulder widths

> Reduction/minimization of clear zones

> Sharpening of horizontal curves with advisory speed postings

> Alterations to typical cross sections including:

$ Roadside ditches shallower than normal

$ Sideslopes steeper than normal (in combination with additional guardrail)

$ Use of curb and closed drainage systems, elimination of roadside ditching

$ Retaining walls

> Wetland and wetland buffer restoration/creation

> Wildlife habitat restoration/creation

> Water quality/streambank, stream buffer, lake buffer creation, restoration, and enhancement

> On and Off - site mitigation

> View/scenic enhancement through vegetation management and grading of sideslopes

> Use of guard rail to allow steeper than 1:4 graded slopes, retaining walls or cribbing

> Use of grade separation/bridging/elevated structures etc.

> Separation of vehicular/pedestrian facilities

> Fencing or landscaping for screening or earth berm buffers

> Retrofitting of historical bridges for alternative uses off-site

> Integration of historical features in interpretive facilities, overlooks, etc.

> Light poles and fixtures with downshielded luminaires

> Architectural/Landscape design:

$ street trees

$ use of native materials

$ use of architectural design details

$ pedestrian facilities

$ signage

$ historical design elements

Minor Arterial construction projects should be designed to avoid historic or archaeological resources wherever possible. This may be in the form of avoiding the disturbance of specific sites and structures as well as historic districts or areas where the presence of the road is disturbing to the historic environment. Many Arterial Roads pass through city, town, and village centers and designers must contend with environmental constraints to fit roadways within historic environments.

Where Minor Arterials pass through historic town centers these standards allow for reduction in lane and shoulder widths as appropriate to avoid the imposition of wide road sections through historically sensitive areas and to preserve, in most cases, the character of the community. Additionally, speed management strategies should be considered to allow the community street networks to safely function with the Minor Arterial system.

Providing curbs along Minor Arterials in historic centers will allow both improved pedestrian safety as well as a reduction in clear zone requirements. Street trees and other urban streetscape elements are essential parts of these roads. Every effort should be made using design enhancements, to integrate the Minor Arterial with the local historic environment.

Minor Arterial construction projects should be designed to avoid natural resources wherever possible. This may be in the form of avoiding disturbance of specific sites or areas where the presence of a road conflicts with the natural ecosystem. Where avoidance proves unfeasible, every effort should be made to minimize impacts and pursue mitigation strategies and design enhancements to enable maximum integration of the Minor Arterial with the natural landscape.

All Minor Arterial projects should consider the presence of environmental resources in project planning, design and construction. The following resources are protected by Federal law:

> Wetlands, lakes, rivers and streams and their shorelines

> Water supplies

> Groundwater protection areas

> Watershed protection areas

> Agricultural districts and farmland

> Floodplains/ways

> Critical wildlife habitat and natural areas

> Rare and endangered species

> Designated AWild and Scenic Rivers"

> Local Conservation districts or zones

> State and Federal forests and wildlife management areas

> Outstanding Resource Waters

Minor Arterial projects should be designed to avoid public recreational facilities wherever possible. Where avoidance proves unfeasible, every effort should be made to minimize impacts including mitigation strategies and design enhancements to enable the maximum integration of the Minor Arterials with the resource. Examples of Recreational Resources include:

> Federally owned, funded, or managed property

> State owned, funded, or managed property

> Locally owned parks and recreational areas

> Privately owned recreational facilities open to the public

> Trails and Greenways

Minor Arterial projects should consider scenic and aesthetic issues for projects that possess scenic qualities. Assessment of scenic qualities should be completed in the Project Development Process. This includes, but is not limited to "Designated Scenic Roads" or "Scenic Byways" as well as other roads with scenic attributes. Techniques for preservation of scenic resources should be employed for views seen from the road, as well as views of the road from surrounding areas. Given that many of the State's Minor Arterials are tourism routes as well as transportation routes, integrating roadway design with visual and safety issues is very important. Additionally, some of these roads travel through dramatic landscapes where dominance of the road could negatively impact scenic values. The following additional techniques should be considered where scenic views from the highway are identified:

> Tree removal or trimming to preserve or enhance views.

> Scenic turnouts where demand is apparent.

> Sculpted ledge to afford natural-like clefts and appearance.

Many of the Minor Arterials in Vermont enter and pass directly through towns, villages or cities. These standards are specifically designed to allow greater flexibility and reduce the conflict with the small scale of many of the affected communities along Minor Arterials. The following guidelines may be appropriate at such locations:

Creative design should integrate economic issues where transportation needs of people, goods and services are significant, and where design of the roadway may affect the vitality of a downtown, commercial or industrial area. In these cases, the following additional guidelines may be appropriate:

> Use appropriate turning radii for large commercial vehicles at appropriate intersections.

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