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Standards & Guidelines


A Brief History

Design standards and guidelines as they apply to great streets, are the result of decades of research, observation and experience. The need for standardization of streets became clear as the role of the private automobile became central to the culture evolving out of the 1950s. Standards helped create a safe, cohesive transportation network in the face of rapid expansion.

How wide should streets be? How fast should automobiles be allowed to travel on them? What elements shall be permitted on the roadside? What constitutes a safe street? How shall we evaluate alternatives for a new street, and how shall we deal with their respective impacts? What types of materials should be used to build our streets, and what are their specifications? These are just a few of the questions that the transportation industry has grappled with since the dawn of the automobile age.

One size fits all? Policies and standards that address these questions usually begin at the national level. Groups like the American Association of State Highway and Transportation Officials (AASHTO), the Federal Highway Administration (FHWA), the Transportation Research Board (TRB), and many others have developed voluminous amounts of information intended to guide the planning and design of our transportation systems.

From the national level, this guidance trickles down to the states and municipalities across the country. They often then build specific guidance from these national resources. The typical end-result of these efforts is a set of "standards" intended to control the planning and development of streets across the respective jurisdictions, e.g. the IDOT Bureau of Design and Environment manual or the St. Louis County Design Criteria Manual. Over time, we have refined these standards to reflect the changes in the transportation industry: larger vehicles, increased reliance on heavy trucks, faster speeds, etc.

It is important to point out one of the indirect results of this evolution: the planning and engineering professions grew very standard-oriented. We as an industry grew to believe that everything had to meet "the standards". Take a look at the shelf in any planner's or engineer's office today, and you will undoubtedly find numerous volumes of standard regulations and practices. If the standards called for 12-foot-wide lanes and 50' setbacks, then that is what would be built. If the standards prohibited certain amenities along the roadside for a certain facility type, then they were not allowed. If the standards were not met, a lengthy "design exception" process often ensued. Obtaining such an exception often required detailed justification to warrant such a deviation from the standard, and in most locales such exceptions were deemed undesirable. Meeting the standards became an integral part of the planning and engineering professions.  


Standards become flexible. Today we are beginning to think differently about "standards". They provide tremendous value, no doubt; however, the industry is now reminding us that the "standards" are not "mandates". Federal guidance is very clear on this. The AASHTO Policy on Geometric Design of Highways and Streets (often referred to as "The Green Book") has traditionally been looked to as the primary guidance document from which many state and local design manuals are developed.

While this text is an excellent reference and resource for the transportation community, it is also unequivocally clear in stating that it is flexible. This point has been so overlooked that AASHTO itself recently published a separate text entitled "A Guide for Achieving Flexibility in Highway Design" to remind the transportation industry that planning and design guidelines made in the "Green Book" are flexible. This is not to say that the "Green Book" should not be consulted; quite the opposite in fact. But every individual situation (in this case every individual street) is different and requires careful planning and design to develop the most appropriate solutions.

Great streets are by their very nature at the center of this discussion. Why? Because they are different. There is no set of standards on a shelf that we can take and apply to a roadway in Ballwin or Belleville or St. Louis and expect a great street to result. To create great streets we must approach each individual place as just that: an individual place with unique characteristics affecting its performance as a transportation route, as a place for pedestrians, as a magnet for development, and as a community resource. To create a great street, we must seek to understand these characteristics before we jump to conclusions about what planning and design guidelines may or may not apply.

Great streets require judgment. However, while there is no one-size-fits-all solution for great streets, there are some characteristics inherent to great streets in most place types that can start us off in the right direction as we seek to determine appropriate planning and design solutions.

  • Space allocation. Most places in the urban and suburban environment are constrained by limited space. As a result, expansion and widening are difficult to accomplish without significantly impacting the existing built environment. The limited space available requires us to allocate the use of that space judiciously with respect to the abutting land uses and surrounding community.
  • Multiple modes. Great streets encourage and prioritize multiple modes of travel. As such, it is important to remember that most historical "standards" were developed with a bias toward automobile travel. Other modes of travel, such as pedestrian, bicycle, and transit, should be fully considered in the planning and design of great streets, not afterthoughts or "retrofits". Failing to plan for these other modes will create "unfriendly environments" for users. The end result will be that other modes of travel will not be able to offer safe, efficient choices to travelers, contributing to the already problematic auto dominance that is preventing the development of great streets. The automobile is still an important mode of travel, but it should be one of several attractive modal choices for travelers along great streets.
  • Multiple needs. Streets provide space for the movement of people and goods. This fundamental need must not be neglected. It must, however, be balanced with many other needs to establish a sense of place. Those needs must be considered at the very early planning stages in order to achieve successful implementation. Some communities may have a need for transit; others, a need for pedestrian facilities. Nearly all will have economic and social needs. Understanding the place-specific needs is essential for success. By working with agencies, businesses, stakeholders, and community citizens we will develop solutions that seek to meet the needs of the place.
  • Safety. Regardless of the type of place in question, safety is always a relevant concern. When it comes to great streets, safety for all users is of paramount importance. Pedestrians, bicyclists, transit users, and automobiles must have facilities that are safe for their respective needs. See the Safety section of this guide for more details.