Transportation Plan


Corridor Design Parameters

Roadway corridors are designed to provide the type of services and perform the functional duties necessary to fulfill its role in the transportation system.  Design parameters are established and applied to achieve relatively safe and efficient operations, conformance with surrounding land uses, and sensitivity to natural environment.  To achieve and maintain a balanced transportation system that meets the needs of the various transportation users, special consideration is necessary to accommodate the different transportation modes and trip types.
 
Roadway Functional Classification begins to define the design parameters of any particular roadway corridor in the network.  Roadways serve different functions and are to be designed relative to the type of service they provide.  Two primary design parameters that affect a roadway’s ability to function as necessary include the Design Vehicle and Design Speed.   

 

Below is a summary of design vehicle and speed guidelines for the different roadway functional classifications in Northfield:

Table 2.4.1: Design Vehicle & Design Speed Guidelines
  Design Vehicle Design Speed
Minor Arterial WB-50 34-45 mph
Major Collector S-BUS-36 30-40 mph
Minor Collector S-BUS-36 30 mph
Local Street S-BUS-36 25 mph

 

The Design Vehicle establishes the largest vehicle a roadway is designed to accommodate without encroachment on opposing traffic.  While vehicles come in all shapes and sizes, the design vehicle sets operational characteristics, such as turning radii, to which the roadway is designed.  Generally, the design vehicle most affects the design of roadway intersections but applies throughout the roadway corridor.

 
The Design Speed establishes various geometric design features of a roadway with respect to topography, adjacent land use, and intended function of the roadway.  Design features such as curvature and sight distance are directly related to, and vary appreciably with, design speed.  The selected design speed should be consistent with the speeds that drivers are likely to expect on a given roadway corridor, relative to its intended function and physical limitations.  A pertinent consideration in selecting design speeds is the average trip length.  Since Minor Arterials and Major Collector are expected to accommodate relatively longer trips at a higher degree of mobility, recommended design speeds are higher than those for Minor Collectors and Local Streets. 

 

The City’s Comprehensive Plan recommends a set of development principles and a conceptual land use plan illustrating the form, pattern, and character of future development and redevelopment. Within the land use plan, city streets are guided to provide an attractive public realm that better connect places in the community, serve neighborhoods, and better serve non-motorized forms of transportation.  Building upon the context established by the Comprehensive Plan, roadway design guidelines are provided to achieve the desired role of city streets within the community as well as provide the intended function within the roadway network.  The Street Types, established by the Comprehensive Plan, set the context of the cross sectional view of particular roadways in the City of Northfield.