By Barry Waite and Alex Rocco, City of Carson, California
Pavement management programs can save a community significant money. Current programs not only analyze and prioritize maintenance needs, they can even create project cost estimates and analyze various funding scenarios.
Because it lacks a spatial component, a pavement management program is greatly limited. A GIS can add tremendous functionality to a pavement management program not only in graphical output but in analysis, planning, reporting and other areas. This paper describes the City of Carson's experience in integrating GIS and pavement management.
GIS and Pavement Management:
A Concrete Relationship
Introduction
Why is pavement management important?
The replacement value of 100 miles of residential streets is approximately $42,000,000. The City of Carson has 206 miles of streets, many of them multi-lane highways with a much higher value. The investment is huge, and preventative maintenance protects that investment. One dollar spent at the right time can save five dollars later, with a slurry seal now protecting a street from water intrusion leading to potholes and substructure breakdown. The question when to maintain a street is as important as which streets to maintain.
Poor streets project a bad image for a city, especially when the city is trying to encourage businesses to locate or remain in the city. Infrastructure decline is a form of blight that can quickly spread. On the other hand, good infrastructure can act as a catalyst for improvement of an area. Pavement management is certainly not the most glamorous function the city performs. In fact, it places somewhere between trash hauling and tree trimming. If it is not done properly, everyone can tell. To put it bluntly, can any community afford anything less than a formal pavement management program?
The City of Carson is merging a pavement management system, PM+ by CHEC Engineering Consultants, with the city's ArcView based GIS. The two work together to use their strengths. This paper describes some of the things that city staff has learned in the process.
The start of formal pavement management
Until recently, there was a major communication gap between what public works officials knew they needed to protect a public agency's most costly deteriorating asset and the elected officials who control the resources. In 1972, California Governor Brown asked how much money the state needed to protect the existing highway network. No one had an answer. A CalTrans task force developed a pavement management program to answer that question. The purpose was to get trust of the elected officials, quantify the needs and close the communication gap.
A pavement management program quantifies and prioritizes the pavement needs of a region or community. Crews gather information on the condition of the pavement through visual rating and the use of specialized equipment. The result is a recommended treatment for each section, such as slurry seal, overlay, reconstruct or - everyone's favorite - do nothing at this time. By adding information on the average cost of materials for the jurisdiction and the size of the area, the system creates a cost estimate for the treatment.
At budget time, having a report based on sound and objective criteria goes a long way with elected officials and the public. It also helps answer the public's question that has long brought fear to public works directors around the country: "When are you going to fix my street?" People appreciate knowing street maintenance is following a methodical plan designed to conserve their streets and their tax dollars at the same time.
Without GIS, pavement management programs don't tell the whole story
While the pavement management information is useful, interpreting it is difficult, even for the civil engineers who work with it. With the advent of inexpensive and easy to use GIS software, pavement management can go visual. Early links between GIS and pavement management programs aimed solely to map the data, which is certainly very useful. As is so often the case though, GIS ends up being capable of much more.
GIS does more than make pretty maps (but those are nice too)
Analysis
Relate data to any geographic feature
How many square feet of the streets to be slurry sealed is in the redevelopment project area or central business district? ArcView can quickly pick out the area and pass it back to the pavement management program. Without GIS, each street segment would have to have an attribute for redevelopment, transit routes, planning study areas and any other geographic descriptors.
For the City of Carson, streets along mass transit routes can be maintained with funds from a transit related sales tax. ArcView can identify those streets. At the same time, it is simple with ArcView to change a truck route and pass the information to the pavement management program, where designation as a truck route changes the deterioration rate and the corrective action indicated.
Overlay projects with other activities to avoid conflicts
A GIS-related construction permitting system catches potential conflicts with planned street improvements, maintenance, median island construction and new development. The discussion below about the capital improvement program shows some of the potential problems. On a day to day basis, GIS can show if a utility company's plan to dig up a street will conflict with a maintenance plan. If possible, the utility and the city can coordinate their efforts, with the maintenance after the pipeline installation or other work. The result is savings for everyone involved and a more structurally sound street, not to mention a better looking street.
Evaluation of past pavement rehab activities
Use GIS to show areas repaired in previous years and see if the pavement management program's predictions were correct. Also look at areas where, probably due to lack of funds, the program indicated maintenance actions, but the city took none. Did the area hold up or deteriorate as predicted? The results can help adjust the models in the pavement management program to better predict actual conditions.
Overlaying the rate of deterioration with other factors can determine the potential cause of rapid deterioration. It may show trucks using the wrong routes, poorly timed signals pushing more traffic onto residential streets or soil problems creating an unstable substructure.
Capital Improvement Program
Easier visualization of planned activities
A capital improvement program (CIP) contains all of the public works and building projects a city is planning for a given period of time. Carson has a five-year program that the Council reviews every two years. Mapping the CIP makes it much easier for the public or other casual reader to quickly understand the city's plans. The pavement management program creates a priority listing of many of the projects in the CIP.
Avoid conflicts
Don't repair a street in 1998 and reconstruct the sewer under it in 1999. Not only does it damage the pavement, it looks bad. Citizens assume there is no coordination of activities, and they are right. Local governments involve many people in many departments and functions. GIS helps coordinate their activities by overlaying the projects of the various work areas to show overlaps. Work under the street first, then do the street. A street that has been excavated for a pipeline and then repaired does not have as long a life as a street that received a resurfacing of some kind for the entire street following the excavation. GIS helps schedule projects to ensure they are done in the correct order. Other agencies, such as utilities, can receive a copy of the CIP to see how their planned activities may conflict with scheduled city projects. For the City of Carson, utilities are the largest source of conflicts with pavement management activities.
Cluster projects
Clustering allows for economies of scale. Why overlay two streets in 1999 and an adjacent street in 2000? It increases the disruption and gives the area a piecemeal look. Combine adjacent projects to improve the overall appearance of an area. Material costs are not reduced, but labor becomes more efficient with a few large projects instead of many small ones. If a consultant designs the project, the city can have further economy of scale savings and reduce administrative costs.
Spreading funds too thinly, by doing a little work in many places, may be what the pavement management program recommends based on existing conditions. Lacking any spatial component, the pavement management program may scatter projects throughout the city. While the selections may be well reasoned, they do not give that impression to the public. GIS adds the spatial component to bring together adjacent projects that might otherwise be spread over two or three years. The result is less money spent to maintain more streets with a better overall appearance. Combining street projects with sidewalk repair and tree trimming in an area can give the neighborhood an infrastructure facelift (new term, you heard it here first!).
Maps
Pavement condition
Prediction modeling can show streets deteriorating over time with varying funding levels. The results are dramatic. Decision makers can see what will happen if they increase or decrease funding levels, delay a project or change from an overlay to a slurry seal.
This map shows recommended maintenance for a large residential neighborhood in the city. Treatment ranges from slurry seal to an overlay to a full removal and reconstruction.
This is the same area with projected maintenance requirements if no action is taken in the next five years.
Few areas can now get by with a slurry seal, and many need expensive reconstruction.
Annual and long-range maintenance plans
In a recent project, the city slurry sealed, overlaid or reconstructed all of the streets in a large residential area. In ArcView, the street segments were tagged with green for a slurry seal, yellow for an overlay and red for a full reconstruction. The resulting map showed clearly the maintenance plan and the comparative amount of each treatment. Not only did staff and the public find the map useful, the contractor used it for planning purposes.
The pavement management program can project future pavement conditions, either with or without suggested street maintenance taking place. It answers the question, "You want $1,000,000, but what if you only get $500,000?" The program will make projections for costs showing how much more repair will cost if spread out over time. At that point, decision makers can make an informed determination of how much to spend and when. Mapping the change in condition makes for a dramatic presentation - at least as dramatic as it gets when it comes to asphalt.
Other maps
Traffic volumes and functional classification are two byproducts of a good pavement management program because they are two of the elements that determine a street's deterioration rate. Truck routes also are important. Maps of striping plans, detector loops, manholes and water valves assist in determining the cost of a project and for the contractor to replace or deal with following putting down new pavement. All of these are useful in other areas, both as maps and data layers useful elsewhere in the organization's GIS.
Reporting
Priorities
ArcView can build much better reports than can a pavement management program by itself. Attaching a spatial component makes the data much more readable and understandable. Showing priorities in a map makes finding a particular location much faster for any user.
Projected need by area
A pavement management program cannot break a community into geographic regions unless each street segment contains geographic attributes, such as location in a redevelopment area. Not only is entering such data difficult, it is unnecessary. Feed the entire database over to the GIS, select out records by area and feed it back to the pavement program for further analysis to take advantage of the strengths of each program. Alternatively, use the GIS to set the attributes for each segment. However, doing so creates a very large and unwieldy data set that is difficult to manipulate and update. The discussion below regarding dynamic segmentation addresses the issue.
Projects by funding category
As discussed earlier, location can determine the available funding for a particular segment. For the City of Carson, categories include redevelopment, transit routes, bikeways and Community Development Block Grant areas. ArcView selects out these areas and passes them out to the pavement management program to determine the amount of funding by type. Since much of the city's money for each year is in these designated funds, it makes sense to maximize their usage.
Create mailing labels for planned street projects
Simplify the process for notifying residents and businesses of coming actions by letting ArcView create mailing labels. The pavement management program has no facility for creating labels, since it does not include addresses. The most difficult part of the process is simply stuffing envelopes. Careful though, those paper cuts can be nasty.
Relationship to other GIS components
Pavement management provides an excellent opportunity to leverage the organization's data investment. Why should more than one part of an organization collect the same data? For the City of Carson, streets, traffic volumes, street classifications, transit routes, Community Development Block Grant target areas and many other items useful to pavement management were already part of the GIS. Pavement management provides a good opportunity to follow the GIS philosophy of gather the data once and use it in many places.
At the same time, the city used the project as an opportunity to gather street data that other areas in the organization could use. For pavement management, the consultant needed the street width (gutter-to-gutter). For a small additional cost, the consultant measured the curb-to-curb width and total right-of-way. As long as the crews were going out, it made sense to collect sidewalk condition (including the absence of sidewalk), catch basins, water valves, manholes, traffic signals, street lights and all of the signs in the public right-of-way.
A GPS unit could have given the inventory a higher degree of precision, but
it really is not difficult to find a traffic signal or speed limit sign, so the city used
estimated positions. Maybe next time…
Now the city has an inventory of stop signs, directional signs and everything else the city maintains. The inventory will serve as the starting point for a proposed maintenance management system.
Traffic flow data is useful for economic development. Retail businesses are especially concerned with daily traffic volumes. Who would think that pavement management and economic development would use the same information?
Dynamic segmentation
This is a bit abstract, but it is vital to making a pavement management system maintainable. The key to effectively linking pavement management to GIS is dynamic segmentation.
Maintenance and manipulation of data related to linear features such as streets and waterways in GIS is a difficult task. Along a linear feature, starting and ending points of different attribute descriptions rarely coincide. Pavement management provides an excellent example, with events such as widths, conditions, and the numbers of lanes found at different locations along a road. The linear feature representing the road would have to be broken into many segments in the GIS to accurately represent these events and then continuously segmented as changes occur with the pavement. The user is likely to run into storage and processing problems. Dynamic segmentation allows the user to represent events without modifying the linear feature at all.
In dynamic segmentation, a route is created to model the linear feature. Routes are associated with a measurement system, which describe distances along the route. Attributes, or events, are related from their respective table directly to any position along the route as often as the user would like without ever affecting the original linear feature.
Getting started
Preheat oven to 350�, grease a 9" x13" pan, wear safety glasses, ensure adequate ventilation and read all instructions before starting.
Determine the data needed for pavement management
What do you already have? For data you need, what degree of accuracy do you need? Remember that accuracy costs money. Commercial sources may be available to suit your needs, such as for a street data set. Or, this may be an opportunity to create a good data set with high positional accuracy from other sources, such as digital orthophotos. The City of Carson used a street file created from the Los Angeles County Assessor's Office parcel maps.
Data collection and manipulation
Do it yourself or hire a consultant. Most organizations hire a consultant to compile the condition information quickly and inexpensively, although the consultant normally trains city staff to gather updates in the future. The next step is perform the dynamic segmentation. The City of Carson uses ArcInfo to do the segmentation. Lacking ArcInfo, the consultant could perform that function. Then it is up to the pavement management program to analyze the data and attach it to the dynamically segmented route. Let the maps begin!
As long as you're at it, other data to collect
Don't forget it is cheap to gather additional data if the crew is already out there. It may be possible to use other funding sources because it is part of the overall project.
Conclusion
It has been a surprisingly interesting project, with more than a few surprises of "We can do that? Great!" Integrating pavement management and GIS provides dividends for both, especially by providing data to each other that would otherwise be unavailable or unaffordable. Of course, many communities still have their street maintenance supervisor pick out a few spots each year for major rework and assume they got the right ones. But what about planning for other street maintenance and prioritizing to get the maximum benefit for the investment. By using GIS with pavement management in the City of Carson, city management knows its maintenance program is cost effective and is addressing the city's needs.
A street should be more than a collection of potholes
connected by small sections of asphalt.
The authors wish to thank their fellow staff members at the City of Carson and CHEC Engineering Consultants for their patience and assistance in developing this paper.
Barry Waite is the Administrative Analyst for the City of Carson Engineering Services Department, he can be reached at bwaite@e-mail.carson.ca.us.
Alex Rocco is the GIS Analyst for the City of Carson, he can be reached at arocco@e-mail.carson.ca.us.