Pavement management is more than software
City of Kansas City, Missouri's Comprehensive Pavement Management Program
Jeff Martin, Acting Assistant City Engineer, and Greg Rokos, City Engineer, City of Kansas City, Missouri
In today's world of technology many in the public works field may identify "Pavement Management" with the software tool that is used to facilitate part of the process. But true pavement management requires more than the latest computer software. The goal of pavement management is to identify a proper road program funding level, and then provide the highest quality network of pavements possible for the traveling public at the available funding level. To accomplish this goal a city must properly plan its road program, select candidate road segments for various types of rehabilitation and maintenance, design the pavement structure for those streets being rehabilitated, conduct quality assurance testing during construction, and manage utility cuts through a permit and inspection process.
The City of Kansas City, Missouri maintains 2,200 centerline miles (5,600 lane miles) of streets. Last year, approximately 360 lane miles were resurfaced and approximately 50 lane miles were slurry sealed. Given this significant pavement preservation program, the City has been focused on building a comprehensive pavement management program for several years. Today, the City conducts annual pavement condition ratings, uses advanced GIS-based pavement management software to help select candidate road segments, maintains their own materials testing laboratory, conducts nuclear density testing to ensure proper pavement compaction, and has a structured utility street-cut process that includes regular inspections of utility patching. This article will describe each component of the City's comprehensive pavement management program.
The City employs four pavement engineering technicians who have the full-time job of conducting pavement condition ratings on City streets. The technicians' goal is to rate one-third of the City's streets each year so that every street is rated within a three-year time period. The technicians conduct walking surveys on the street segments to ensure accurate and consistent ratings.
|GIS-based pavement management system|
The City began using Windows-based pavement management software about ten years ago, and has now moved to an advanced GIS-based system that runs as an extension of Arcview. One value of the system is that it calculates an objective reproducible Pavement Condition Index (PCI) for each pavement segment based on the pavement condition ratings. The PCI provides a consistent measure that City staff can use to communicate with residents and politicians about why certain roads are selected to be included in the pavement preservation program each year.
Whereas in the past, when the City selected candidates for its resurfacing, slurry seal, and crack sealing programs based primarily on the number of years since the last treatment on the street, the City can now use the software to select candidate projects in each category based on current condition, estimated traffic, and the relative benefit of each project. The system can also assist the City to estimate proper funding levels for its pavement preservation program.
Once projects have been selected, it is vitally important that quality assurance testing be conducted during construction to ensure that the quality of the materials and construction methods meets the City's specifications. The City uses specifications developed by APWA's Kansas City Metro Chapter. Independent materials labs hired by the hot mix producer develop proposed job mix formula that meet the City's specifications. However, the City maintains its own materials testing laboratory for the purpose of testing materials produced during construction. The laboratory employs six full-time technicians plus an engineer. In addition, four to six seasonal employees are added for the construction season.
In addition to the materials testing laboratory, the City conducts its own nuclear density testing in the field to ensure proper compaction. This is arguably the most important step that a pavement owner can take to ensure that a quality pavement is constructed that will perform as expected. The City's nuclear density gauges are calibrated to hot mix asphalt coming from the asphalt plants each year. Generally, the City takes one density test per paving crew per day so that a rolling pattern that successfully achieves the specified density of 96% of Marshall Density can be determined. Once a successful rolling pattern has been established, the City's full-time inspector monitors the contractor to ensure that the rolling pattern is maintained.
Compaction in action in Kansas City
The City also tests material samples taken at the hot mix plant. One sample per 1,000 tons is tested for asphalt content (using the ignition method), gradation, and maximum theoretical density. In addition, Marshall stability, flow and density are determined.
So, once a quality pavement has been constructed the pavement management job is over—right? Well, not quite. Like many other communities, Kansas City has the challenge of managing utility cuts in city streets. In an effort to proactively manage utility cuts, the city has been divided into three geographic areas for the purpose of managing and tracking utility cuts. Utility cut inspectors have been >established in each of these three areas who are responsible for coordinating the City's paving program with the utilities in that area. The utility cut supervisors and inspectors work in the pavement preservation section so that they have first-hand knowledge of the City's paving plans.
The City's permit system notifies the utility cut supervisors when an excavation, traffic control, or a plate permit (for a cut to be open longer than one day) is taken out. A degradation fee is applied such that the cost of cutting a new pavement is higher than the cost of cutting an older pavement. The utility cut supervisors maintain the permit records until they accept the permanent patch and close out the permit.
The City of Kansas City's comprehensive pavement management program should serve as a model for other communities trying to "do the right thing at the right time in the right place in the right way" to preserve the quality of their pavements. Please feel free to contact the authors at firstname.lastname@example.org or email@example.com to obtain more information about any part of the City's pavement management program.
Gordon Daring, P.E., APWA Engineering and Technology Committee Chair, contributed to this article.