Standards

The Minnesota Department of Transportation (Mn/DOT) has developed a screening method for identifying potential carbon monoxide (CO) "hot spot" locations in the seven county Twin Cities Metropolitan Area. Of five models evaluated, a modified Canyon Model was selected as being most representative of urban developed conditions for prediction of dispersion and concentration of CO. The HIWAY 2 model is recommended for other, more open areas. These recommendations are based on a comparative evaluation of the models' ability to forecast monitored CO concentrations at a historical "hot spot" (a location where ambient CO concentrations are high and may exceed the National Ambient Air Quality Standards) in the Minneapolis CBD. This study utilizes both U.S. EPA "Hot Spot" screening procedures as well as the newly developed Mn/DOT techniques to reassess the State Implementation Plan's (SIP's) predictions of "attainment" of the 8-hour ambient CO standard in the Twin Cities Area by the end of 1982.

Supplements 3 and 4, effective March 1, 1940, are supplements to Specifications for Highway Construction, July 1, 1938.

This Technical Summary pertains to the LRRB-produced Report 2013-31, “Implications of Modifying State Aid Standards: Urban Construction or Reconstruction to Accommodate Various Roadway Users,” published December 2013.

The degree of modal split in the United States has continued to change with increased use of non-motorized modes. To accommodate a variety of users, context-sensitive solutions are being pursued. Such solutions call for the sharing of right-of-way by multiple user groups with different and often competing demands. Traditionally, the needs of vehicular traffic have been prioritized as evident in many current design standards. This research focuses on developing guidance for design decisions to best balance the competing needs and accommodate all expected roadway users. Non-standard design solutions, often associated with complete streets, were investigated in two major contexts. The first involved a comprehensive review of the current-state-of-the-practice in design standards, complete streets, and associated legislation in Minnesota and nationally. Second, a detailed analysis of 11 'complete street' study sites was conducted. The study primarily focused on evaluating changes in safety and operations between the periods before and after implementation. Differences in the characteristics of the study sites and varying degrees of changes and improvements conducted at each site prevented an aggregate quantification of the implications of complete street improvements across all sites, and specific recommendations for changes in design standards. Nevertheless, the analysis of complete street designs implemented at the 11 study sites suggest that changes made to these study sites did not result in adverse safety or operational impacts. Therefore, providing flexibility and modification to the State Aid Design Standards in the context of complete streets and conditions specified in this research appears to be a reasonable consideration.

With increasing traffic being carried by residential streets, combined with the negative effects of climate on pavement material durability and strength and damage due to frequent cutting and patching of the roadway pavement to allow for the placement of utilities, residential streets are requiring more frequent, extensive, and costly maintenance and rehabilitation (M&R). Also, the pavement design life is significantly reduced. The increased cost of M&R and eventual reconstruction is an added burden on already limited city budgets. To rectify this situation, city managers and engineers are analyzing the difference in cost over a 30 year life-cycle for 9- to 10-ton design standard compared to a 5- to 7-ton design standard. Adopting a more significant pavement structure does, however, have significant cost implications, as the initial cost of the pavement is expected to rise significantly. This increase in cost is expected to be offset by a significant decrease in M&R costs and an increase in pavement life that will delay eventual reconstruction. The Minnesota Department of Transportation (MnDOT), on behalf of the Local Road Research Board (LRRB), initiated this study to evaluate the impact of enhancing roadway construction standards to accommodate greater axle loads on local residential streets in Minnesota cities on life-cycle costs. The primary focus of this study was to compare the current residential roadway construction and maintenance life-cycle costs (5- to 7-ton based on construction standards) to the lifecycle costs of residential roadways constructed with 9- to 10-ton standards.