| Advancing Functional Classification to Address Neighborhoods |
| By Ransford S. McCourt, P.E (M), DKS Associates |
| (Presented at 1998 ITE District 6 Annual Meeting in San Jose, California) |
| For the past thirty years communities have developed functional classifications for their roadway systems that is built off guidelines developed by AASHTO in 1964 and reinforced by FHWA in recent publications. In the 1990s, there has been a strong movement to address the livability of neighborhoods and calm traffic. Many cities undertake neighborhood traffic management (NTM) programs as a response to citizen input to reduce speeding and cut through traffic. Many times NTM programs are approached as a separate activity, independent of the community’s transportation plan or functional classification of street. In the Portland area, the Cities of Beaverton, Fairview, Forest Grove, Hillsboro, Happy Valley, Milwaukie, Tigard, Troutdale and West Linn have updated their Transportation System Plans to include a new route in their functional classification system to reflect neighborhoods. |
| All of the Portland area cities had a functional classification map based upon FHWA and AASHTO guidelines passed down from plan to plan over the past 20 years. With the advent of the State of Oregon Transportation Planning Rule (Goal 12), each city was required to update their functional classification as part of their Transportation System Plans (TSP). This paper focuses on the process to determine functional classification of streets developed for these Portland area cities. |
| Functional Classification |
| Functional classification had commonly been mistaken as a determinate for traffic volume, road size, urban design, land use and various other features in the prior plans. These elements represent the form of a roadway but not its function. The traffic demand can be more directly related to land use. Typically, a significant reason for high traffic volumes on surface streets at any point can be related to the level of land use intensity within a mile or two. Many arterials with the highest level of connectivity have only 33 to 67 percent "through traffic". Without the connectivity provided by arterials and collectors, the impact of traffic intruding into neighborhoods and local streets increases substantially. Traffic volume, design (including access standards) and size of the roadway are outcomes of function, but do not define function. The objective of the TSP for each city was to update the functional classification of streets and determine the form of streets in identifying the future needs. |
| Some of the cities that have done the most innovative work regarding functional classification (Phoenix and Houston) have developed very complex relationships between land use and functional classification. While land use and street design are critical elements of a roadways form, they do not define its function. The complexity of multiple land use/roadway classifications is difficult for the public to interpret and understand. Therefore, our work in the Portland area focused on structure that was readily understandable by the public and would be approvable by local councils and commissions. |
| Function can best be defined by connectivity. Without connectivity, neither the mobility nor access can be served. Roadways that provided the greatest reach of connectivity are the highest level facilities. Arterials can be defined by regional level connectivity. The regional movement of persons, goods and services depends on an efficient arterial system. The FHWA guidelines define arterials as "providing direct service to long trips". These routes go beyond the city limits in providing connectivity and can be defined into two groups: principal arterials (typically state routes) and arterials. |
| Collectors can be defined by citywide or district wide connectivity. These routes span large areas of a city but typically do not extend significantly into adjacent jurisdictions. They are important to a city’s circulation system. The past planning text books on functional classification then group all other roadways as local streets, providing the highest level of access to adjoining land uses. |
| In our work in the Portland area, it became clear that there was a missing class of roadways in the all the functional classifications - neighborhood route. In many past plans, agencies defined a minor collector or a neighborhood collector; however, use of the term collector is not appropriate. Collectors provide citywide or large district connectivity and circulation. There is a level between collector and local streets that is unique due to its level of connectivity. Local streets can be cul-de-sacs or short streets that do not connect to anything. Neighborhood routes are commonly used by residents to circulate out of their neighborhood. They have connections within the neighborhood and between neighborhoods. These routes have neighborhood connectivity, but do not serve as citywide streets. They have been the most sensitive routes to through, speeding traffic due to their residential frontage. Because of their limited level of connectivity they can commonly be used as cut-through routes in lieu of congested or less direct arterials/collectors which are not performing adequately. Cut-through traffic has the highest propensity to speed, creating negative impacts on these neighborhood routes. By designating these routes, a more systematic, citywide program of neighborhood traffic management can be undertaken to protect these sensitive routes. |
| Process |
| For each of the TSPs, a citizen and technical advisory committee was established. These committees were used in the development of the neighborhood routes. The citizens in particular had detailed knowledge of the routes in each city that neighbors generally used to access their neighborhoods. Mapping homework exercises were designed to engage the committee members and provide a forum for discussion and evaluation as to which routes should be added as neighborhood routes and which minor collectors were more reflective of neighborhood function. |
It was important for the public to understand the meaning of connectivity and how it related to the street function. These classifications did not mean that because a route is an arterial it is large and has lots of traffic (you can have two lane arterials). Nor do the definitions dictate that a local street should only be small with little traffic (for example a local street in an industrial area). This was extremely important in the public’s understanding of functional classification. In the end, the normal contentious debate about what routes were arterials or collectors or local streets was nearly avoided entirely. This was due to the public’s easy understanding of connectivity and the new neighborhood classification. |
| Functional Classification Changes |
| The proposed functional classifications differed from the existing approved functional classifications. Neighborhood routes were not defined in the existing functional classifications. The prior system added major and minor classifications to arterials and collectors. These designations were removed since they define more of the design and demand (which are outcomes of function and land use), but not function. The Portland region MPO (Metro) has developed Regional Street Design guidelines that better define the form of the regional street system. Figure 1 provides a map a the neighborhood routes for the City of Hillsboro, providing an example of the type of route and extent of coverage within the city. |
| Criteria for Determining Changes to Functional Classification |
| The criteria used to assess connectivity has two components: the extent of connectivity and the frequency of the facility type. Maps can be used to determine regional, city/district and neighborhood connections. The frequency or need for facilities of certain classifications is not routine or easy to package into a single criteria. While criteria can be generalized for arterial spacing of a mile, collector spacing of a quarter to a half mile, and neighborhood connections at an eighth to a sixteenth of a mile, this is not the only basis for defining functional classification. Changes in land use, environmental issues or barriers, topographic constraints, and demand for facilities can change the frequency for routes of certain functional classifications. While spacing standards can be a guide, they must consider other features and potential long term uses in the area (some areas would not experience significant changes in demand, where others will). Linkages to regional centers, town centers and station areas are another consideration for addressing frequency of routes of certain functional class. For example, connectivity to these areas is important, whereas linkages that do not connect any of these areas could be classified as lower levels in the functional classification. |
| Characteristics of Streets for each Functional Classification |
| The design characteristics of streets in each city were developed to meet the function and demand for each facility type. Because the actual design of roadway can vary from segment to segment due to adjacent land uses and demands, the objective was to define a system that allows standardization of key characteristics to provide consistency, but also to provide criteria for application that provides some flexibility, while meeting standards. Table 1 provides a summary of the key street characteristics and how they can be applied |
| Summary |
| The functional classification systems for each of these communities were developed through extensive community, staff and interagency coordination. In each of the communities, the citizens commonly held perceptions and fears regarding the functional classification of their streets. There was a large difference between being a local street and the next category up which typically was a collector route. The functional classifications of the past did not necessarily reflect the function of routes. In most cases they relied on measures such as traffic volume, width and speed which relate to the outcomes of the roadways functionality rather than their true function. Working with the communities, it was determined that the actual function of the streets was related directly to connectivity. Using connectivity as a measure of the function of a route, streets were classified based upon the level of service they provided related to connectivity. The other measures commonly used in the past, particularly traffic volumes, were used to size facilities (issues of the form of the roadway) rather than to determine their function. Measures such as traffic volume are outcomes (not functionality) of land use decisions and connectivity. The final result was an easy to understand functional classification system and adopted Transportation System Plans with minimal debate regarding functional classification. |
Table 1: Proposed Street Characteristics
| Attribute | Recommendation |
| Vehicle Lane Widths: (minimum widths) | Truck Route = 12 feet Bus Route = 11 feet Arterial = 12 feet Collector = 11 feet Neighborhood = 10 feet Local = 9 to 10 feet Turn Lane = 10 feet |
| On-Street Parking: | Residential = 6 to 8 feet Commercial = 7 to 8 feet |
| Bicycle Lanes: (minimum widths) | New Construction = 6 feet Reconstruction = 5 to 6 feet |
| Sidewalks: (minimum width) | Local = 5 feet Neighborhood = 5 feet Collector = 6 to 8 feet Arterial = 6 to 10 feet |
| Curb Extensions for Pedestrians: | Consider on any Pedestrian Master Plan Route |
| Landscape Strips: | Residential/Neighborhood = Optional Collector/Arterial = Desirable |
| Medians: | 5-Lane = Required 3-Lane = Optional |
| Neighborhood Traffic Management: | Local = Should not be necessary Neighborhood = Consider as Necessary Collectors = Under Special Conditions Arterials = Only under Special Conditions |
| Transit: | Arterial/collectors = Appropriate Neighborhood = Only in special circumstances |
| Turn Lanes: | When Warranted |
| Access Control: | Goal 3, Policy 8 |
Ransford McCourt, P.E.
DKS Associates
921 S.W. Washington Street, Suite 612
Portland, OR 97205-2824
(503)243-3500