Trucks and trucking

This is the Executive Summary of the findings and recommendations to the Special Refuse Collection Vehicle Committee jointly under the auspices of the State Commissioner of Highways and the Director of the Pollution Control Agency. This Executive Summary is a condensed non-technical version of the final report. It provides a capsulized summary and acts as a guide for future decisions as they relate to the issue of overweight rear loading refuse compactor vehicles under load conditions when collecting or transporting solid waste refuse. The full and final report contains the complete findings, recorded weight datum, identification of contributing factors and suggested recommendations. Readers interested in the more detailed version should refer to the final report.

This report summarizes the approach, findings, and recommendations of the Minnesota Truck Size and Weight (TS&W) Project led by the Minnesota Department of Transportation (Mn/DOT) in cooperation with other public and private stakeholders. The purpose of the project is to assess changes to Minnesota's TS&W laws that would benefit the Minnesota economy while protecting roadway infrastructure and safety.

Over the last several years shipping costs and efficiencies have led to the emergence of larger trucks with increased load capacity. Many of Minnesota's state and county highways were built many years ago and were not designed to withstand the weights of todays larger trucks. Many roads continue to be restricted to heavy vehicles, particularly in the spring when thawing conditions make roadways especially vulnerable to weight related damage. In response to this situation, legislation was enacted in 1985 requiring the preparation of a market artery study to identify the routes, costs and priorities for upgrading the load capacity of the highways which are important to Minnesota shipping. This report documents the first phase of the market artery study conducted by the Minnesota Department of Transportation (Mn/DOT). Market arteries have been identified based on input from counties, cities. Regional Development Commissions and the public. In addition, upgrading needs and costs have been estimated and Mn/DOT District priorities for accommodating 80,000 pound vehicles on identified market artery routes have been determined.

In 1980, Minnesota passed a new law for controlling overweight trucks. This new law allowed bills of lading, weight tickets, and other documents that indicate the weight of a truck to be used as evidence in a civil court proceeding to establish overweight violations. Under many circumstances it is no longer necessary for the State Patrol to catch an overweight truck on the road. A demand for the payment of penalties can be sent out in the mail and if not paid, a civil law suit will be initiated by the state. "Relevant evidence" of such weight documents is now used by the civil weight enforcement group of the Department of Public Safety and is proving to be an excellent addition in the restriction of illegally overweight motor carriage. This report discusses the history of Minnesota weight enforcement and the role of the relevant evidence law in constructing a comprehensive weight enforcement system.

In the past, the major determinant for spring load restrictions was the tested strength of the road. Since trucks are the stressing fraction of the traffic, and they will vary in volume from nearly nothing to many thousand trucks per day, this major aspect must be taken into account. Other diagnostic techniques developed recently (and are in common usage) can be used to aid the establishment of spring axle load.

Spring is a critical period for Minnesota's roads because the roadbed soils and aggregate base materials are in a weakened state during and after the thawing process. Spring load restrictions (SLR) are used as a preservation strategy to reduce damage, thereby protecting Minnesota's investment in the infrastructure. However, the imposition of spring load restrictions impacts industry, both in their operations, and financially. While it is clear that spring load restrictions benefit the infrastructure, there are two issues of which little is known: (1) the economic impacts that result when access to the transportation system is restricted and (2) extent of enforcement efforts. The development of the Spring Load Restrictions Task Force was in response to 1999 legislation requiring the Commissioner of Transportation to establish a task force to study spring load restrictions and report to the legislature its findings and any recommendations for legislative action by February 1,2000. The legislation also calls for task force members that represent many interests including aggregate and readymix producers, agriculture, waste haulers, construction, and logging. Other members representing local agencies, associations, and enforcement have also been included. The task force objectives were to study the current status of spring load restrictions in the state of Minnesota, explore the economic impacts of the load restrictions, and report the findings to the legislature.

Spring is a critical period for Minnesota's roads because the roadbed soils and aggregate base materials are in a weakened state during and after the thawing process. Spring load restrictions (SLR) are used as a preservation strategy to reduce damage, thereby protecting Minnesota's investment in the infrastructure. However, the imposition of spring load restrictions impacts industry, both in their operations, and financially. While it is clear that spring load restrictions benefit the infrastructure, there are two issues of which little is known: (1) the economic impacts that result when access to the transportation system is restricted and (2) extent of enforcement efforts. The development of the Spring Load Restrictions Task Force was in response to 1999 legislation requiring the Commissioner of Transportation to establish a task force to study spring load restrictions and report to the legislature its findings and any recommendations for legislative action by February 1, 2000. The legislation also calls for task force members that represent many interests including aggregate and readymix producers, agriculture, waste haulers, construction, and logging. Other members representing local agencies, associations, and enforcement have also been included. The task force objectives were to study the current status of spring load restrictions in the state of Minnesota, explore the economic impacts of the load restrictions, and report the findings to the legislature.

The Northstar Workshop, "A Bold New Look at Minnesota's Roads and Loads," was held at the Leamington Hotel, Minneapolis, Minnesota on November 13, 14, and 15, 1984. The Workshop addressed two main aspects of highway loads - the 80,000-lb. gross truck load and the springtime load limitation policies. There was an attendance of about 140, mainly from Mn/DOT, but also from the four adjacent states and Michigan, the two bordering Canadian provinces, the Minnesota State Planning Agency and Legislative Research, agencies such as AASHTO and FHWA, the Minnesota Motor Transport Association, county and city engineers, and the paving industry and truck manufacturing industry; thus, it constituted a comprehensive cross-section of persons concerned with the subjects under discussion. The format of the Workshop was one and one-half days of presentation of papers by individuals on subjects which had been assigned to them, with limited questions and discussion after each one, followed by group discussions for which the attendees were divided into six groups. Reports of these discussions were made to the full conference by group leaders and a final summary was made by Deputy Commissioner Robert McDonald. Following the Workshop, Mr. McDonald appointed a Truck Weight Action Group to compile recommendations based on the papers and discussions at the Workshop, and this group has made its report; its recommendations, in effect, represent a summary of the dominant thoughts of the Workshop. The report is included in Appendix A of the proceedings.

The life span of a roadway structure (underlying soil, gravel base, and road surfacing) is primarily influenced by three factors; structure strength, the number of trucks, and the weight of the trucks. Each axle load on a pavement takes away part of the pavement's life. Each unique pavement can take a given number of fatigue or stress cycles from the trucks before that pavement becomes structurally inadequate. In order to understand this interaction between loads and road structures, we need a common denominator for the truck traffic to define the damaging effects of the various weight levels. Such a common traffic damage identifier is needed since all roads carry completely mixed traffic of smallest cars to large trucks. Most states, including Minnesota, now use an expression of N18 - translated mathematically it means the number of equivalent 18,000 Ib. single axle loads. Through years of research we've determined the amount of roadway damage done by any axle weight. A graph (Figure 1) and Table 1 will help to describe this relative damage effect.

This study compares the number and extent of freeway and expressway shoulder encroachments by large trucks on standard width and wider concrete pavements with bituminous shoulders. A total of 486 trucks were trailed a total of 3,241 miles under fair weather daylight conditions. Fewer pavement edge loads and bituminous shoulder loads occurred on the wider pavements.