CHAPTER 1 GENERAL DESIGN GUIDELINES 1.0 INTRODUCTION This Publication has been developed to provide current, uniform procedures and guidelines for the application and design of safe, convenient, efficient and attractive local roads and streets which constitute a high proportion of the roadway length in the Commonwealth of Pennsylvania. These guidelines are intended primarily for use by responsible officials of local governments to formulate highway design criteria, policies and procedures within the appropriate jurisdictional highway classification that does not constitute the State highway system network. Initiative should be exercised to utilize the most appropriate design values within the given ranges based upon the project context and roadway typology wherever practicable and within reasonable economic limitations and sound engineering judgment. In restricted or unusual conditions, these guide values may not be achievable. Every effort should be made to obtain proper drainage and the best possible alignment, grade and sight distance that are consistent with the terrain, development (present and anticipated), safety and available funding. These factors should be recognized before any modifications are made that introduce design exception features. This Publication does not attempt to encompass the total scope of important, published information and literature relative to the formulation of highway design criteria, policies and procedures. Sources of additional publications and related material, which should complement the concepts contained herein, are presented in Appendix B. Since safety is an important factor in all roadway projects, these guidelines were developed giving number one priority to the safety of pedestrians, bicyclists and the motoring public. Pedestrians are a part of every roadway environment and attention must be paid to their presence in urban as well as rural areas. Pedestrian access, safety and needs must be given full consideration during the planning and design of all transportation projects. The Americans with Disabilities Act (ADA) of 1990 is a civil rights statute that prohibits discrimination against people with disabilities. ADA implementing regulations for Title II prohibit discrimination in the provision of services, programs, and activities by state and local governments. Designing and constructing pedestrian facilities in the public right-of-way that are not usable by people with disabilities may constitute discrimination. Section 504 of the Rehabilitation Act of 1973 (504) includes similar prohibitions in the conduct of federally-funded programs. ADA accessibility provisions apply to the entire transportation project development process including planning, design, construction and maintenance activities. However, it may not be practical or possible to obtain obstacle-free roadside areas. Therefore, every effort should be made to provide as much clear roadside width as is practical. This becomes more important as speeds increase. The specific design values and criteria applicable to the local rural road system are presented in Chapter 2 while those applicable to the local urban road system are presented in Chapter 3. The policy of the Pennsylvania Department of Transportation * regarding local roads and streets is presented in these guidelines. However, it should be recognized that the contents contained herein are guidelines and that there are certain conditions which shall require individual consideration. Where a short segment of roadway must be relocated, a higher type design shall not be approved unless the municipality guarantees a definite schedule for similar improvements to the adjacent sections of the roadway. If local officials do not concur in writing to the above, the Department policy shall be to replace in kind. The inclusion of specified design criteria in this Publication does not imply that existing facilities, which were designed and constructed using different criteria, are either substandard or must be reconstructed to meet the criteria contained herein. Many existing facilities, which met the design criteria at the time of their construction, are adequate to safely and efficiently accommodate current traffic demands. * Hereinafter referred to as the Department. 1-1
Since it is not feasible to provide a highway system that is continuously in total compliance with the most current design criteria, it is imperative that both new construction and reconstruction projects are selected from a carefully planned program which identifies those locations in need of improvement and then treats them in priority order. Once a new construction or reconstruction project is selected in this manner, this Publication shall be used in determining the appropriate design criteria. Department-owned roadways provide local roads and driveways with access. Publication 282, Highway Occupancy Permit (HOP) Guidelines, describes laws, regulations, policies, and procedures relating to access for local roads and driveways onto facilities owned by the Department. These guidelines were prepared to assist and provide applicants with general instructions when applying for a Highway Occupancy Permit relating to placing or modifying an access and opening the highway surface. Policies are discussed for situations where Department-owned roadways are reconstructed because an existing access is modified or a new access is provided. Permit applications involving a local road, a medium volume driveway, or a high volume driveway would include the submission of a Traffic Impact Study to the Department for review and approval. 1.1 LAND USE CONTEXT AND ROADWAY TYPOLOGIES Each project's scope shall be based on the well-defined needs that must be addressed. The needs are based upon the most pressing transportation problems in the project area. The scope of work shall be used to determine the appropriate design criteria for all projects. A determination of the roadway's typology should be identified early in project design based on a project's land use context, as well as the functional classification of the roadway. A. Land Use Context. Seven context areas are described below, from the least to the most developed: 1. Rural. This context area consists of a few houses and structures dotting a farm or forest landscape. The areas are predominantly natural wetlands, woodlands, meadow or cultivated land. Small markets, gas stations, diners, farm supplies, convenience grocers, etc. are often seen at the intersections of arterial or collector roads. Rural areas also may include a few commercial or civic uses and a number of homes close to the roadway. 2. Suburban Neighborhood. This area is predominantly low-density residential communities. House lots are typically arranged along a curvilinear internal system of streets with limited connections to regional road network or surrounding streets. Lot sizes are usually 0.8 ha (2 acres) to 0.1 ha (0.25 acre), but in older suburbs, it is common to find 0.05 ha (0.125 acre) lots. Garden apartments are also included in this type. Neighborhoods can include community facilities such as schools, churches, recreational facilities, and some stores and offices. When suburban houses line an arterial roadway but have their primary access to frontage roads or rear access roads, it is possible to classify this area as a "suburban corridor". 3. Suburban Corridor. This area is characterized by big box stores, commercial strip centers, restaurants, auto dealerships, office parks, and gas stations. These uses are sometimes interspersed with natural areas and occasional clusters of homes. Buildings are usually set back from the roadway behind surface parking. Office buildings are usually set back a bit more than adjacent retail frontage to establish garden separation from ground windows. 4. Suburban Center. This area is often a mixed-use, cohesive collection of land uses that may include residential, office, retail, and restaurant uses where commercial uses serve surrounding neighborhoods. These areas are typically designed to be accessible by car, and may include large parking areas and garages. They are less accommodating to pedestrians than town centers, and opportunities to cross the primary roadway can be limited. On-street parking may or may not be provided. 5. Town/Village Neighborhood. This area is predominantly residential neighborhoods, sometimes mixed with retail, restaurants, and offices. In urban places, residential buildings tend to be close to the street. Rowhouses fronting the sidewalk, and houses back 9 m (30 ft) behind a front lawn are both common types. Small retail establishments sometimes occupy principal corners. Block sizes are regular and often small in comparison to suburban neighborhood blocks. Even where streets are narrow, on-street parking is common and typically well used. The large majority of neighborhoods have sidewalks. 1-2
6. Town/Village Center. This area is a mixed use, high density area with buildings adjacent to the sidewalk, typically two to four stories tall with commercial operations on the ground floor and offices or residences above. Parallel parking usually occupies both sides of the street with parking lots behind the buildings. Important public buildings, such as the town hall or library, are provided special prominence. 7. Urban Core. These areas are downtown areas consisting of blocks of higher density, mixed use buildings. Buildings vary in height from three to over 60 stories with most buildings dating from an era when elevators were new technology - so five to twelve stories were the standard. B. Roadway Typologies. Roadway typology captures the role of the roadway within its context, focusing on characteristics of access, mobility, and speed. The Roadway Typologies are illustrated in Table 1.1 and Figure 1.1. The roadway classes shown in Table 1.1 correspond to the classifications of arterial, collector, and local, as described in the 2004 AASHTO publication, A Policy on Geometric Design of Highways and Streets *. Once the roadway typology is determined, the appropriate design criteria can be selected. See Chapters 2 and 3 for guidance. As stated in Section 1.0 above, initiative should be exercised to utilize the most appropriate design values within the given ranges based upon the project context and roadway typology wherever practicable and within reasonable economic limitations and sound engineering judgment. ROADWAY CLASS Arterial Arterial Collector Collector Local ROADWAY TYPE Regional Community Community Neighborhood Local DESIRED OPERATING SPEED 50-90 km/h (30-55 mph) 40-90 km/h (25-55 mph) 40-90 km/h (25-55 mph) 40-60 km/h (25-35 mph) 30-50 km/h (20-30 mph) TABLE 1.1 ROADWAY TYPOLOGIES AVERAGE TRIP LENGTH 24-56 km (15-35 mi) 11-40 km (7-25 mi) 8-16 km (5-10 mi) < 11 km (< 7 mi) < 8 km (< 5 mi) VOLUME 10,000-40,000 5,000-25,000 5,000-15,000 < 6,000 < 3,000 INTERSECTION SPACING 200-400 m (660-1,320 ft) 90-400 m (300-1,320 ft) 90-200 m (300-660 ft) 90-200 m (300-660 ft) 60-200 m (200-660 ft) COMMENTS Roadways in this category would be considered "Principal Arterial" in traditional functional classification. Often classified as "Minor Arterial" in traditional classification but may include road segments classified as "Principal Arterial". Often similar in appearance to a community arterial. Typically classified as "Major Collector". Similar in appearance to local roadways. Typically classified as "Minor Collector". * Hereinafter referred to as the 2004 AASHTO Green Book. 1-3
FIGURE 1.1 ILLUSTRATED ROADWAY TYPOLOGIES 1-4
FIGURE 1.1 (CONTINUED) ILLUSTRATED ROADWAY TYPOLOGIES 1-5
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