Memo Pavement Investment Guide

Transcription

1 Memo Pavement Investment Guide Date: 03/26/2018 To: District Engineers, Assistant District Engineers for Program Delivery and Maintenance Operations, District Materials Engineers, District Planners From: Glenn Engstrom, P.E. Director, Office of Materials and Road Research Purpose Our pavement system is a complex network of 14,302 total roadway miles. Given the current state of repair of the system, it has a value of about $4 Billion. In 2000, the value was about $5 Billion. MnDOT currently spends around $ 300M a year to keep it in a serviceable condition. The pavement system is very complex structurally with a variety of materials, thicknesses and moisture conditions throughout each of the seasons of the year. Traffic loading also varies from the high volume Interstate to the low volume State highways. We also have a large number of rehabilitation techniques that we can use to repair the roadway. All these factors must be considered when we determine the final repair technique. MnDOT s process for selecting pavement rehabilitation types is decentralized. The Office of Materials and Road Research (OMRR) currently identifies potential projects by analysis of road history and current conditions, with the pavement management system. The list of potential projects is sent to each District where they modify the list to better fit their needs and use more detailed information that they have available. The resulting modified project list is then compared to the statewide performance goals. Further project scoping will examine potential issues affecting costs and project schedules. Finally, specific pavement alternatives for each project are reviewed through a life-cycle cost analysis. District staff have the ability to make the best decisions on pavement investments. They also are in the best position to use the information noted above to make investment trade off decisions with the other transportation assets. The goal of this Pavement Investment Guide is to provide MnDOT District decision makers new tools to optimize the performance of their pavement system. The OMRR is creating a simple, easy to use, guide with associated software and commentary on the why and how, not just a cookbook. A vital part of this effort involves the creation of new measures that will help make more informed decisions. In addition, the Districts will share their investment strategies and resulting performance measure outcomes through a statewide reporting process.

2 Limitations of Current Programing/Investment Process Our current process has a STIP/CHIP focus. As such, the end points are reported, but what happens in between is not considered. There is also a limited focus on vehicle miles travelled. We may be over investing on lower volume roads with fixes that cannot be justified when we look at the entire network. However, special attention needs to be paid to low volume AADT roadways that may be on a critical path for some manufacturing companies, or a life line for underserved communities, etc. The Districts are the best ones to recognize these roadways that need to be given higher priority. Recommended maintenance/pavement preservation schedules are not considered as a part of the process. The cumulative backlog of deferred pavement rehabilitation is not addressed. In addition, more consideration needs to be given to the higher cost to properly rehabilitate roadways as pavement condition gets worse and needs more extensive repair. The current measures for % poor and % good give a good snap shot it time of our pavement performance. However, they are limited in that they don t give a complete picture of the overall health of the system. Investment Philosophy MnDOT needs to optimize our investment at the network level, meaning we must look at our entire system performance and not specifically project by project. MnDOT does not have the funds to construct the optimum fix on each segment of roadway, instead the goal is to maximize the benefits for the entire system. MnDOT has a variety of fixes at our disposal to improve the condition of our pavements. The mix-of-fixes strategy offers us the best opportunity for improvement. Long-term, medium term and preventive maintenance must all be considered to arrive at the best solution. Because conditions vary from District to District the percentage of each type of fix used will vary across the state. Each District is at a different place with the condition of their pavements and as such will need a different strategy to meet performance targets. MnDOT currently has performance targets for % Poor and % Good, and we will continue to strive to meet these for each system. In addition, new FHWA target measures for ride, cracking, faulting and rutting will need to be met. System performance will be measured by four additional measures, or health indicators including Remaining Service Life, Asset Value, Asset Sustainability Ratio, and preventive maintenance. The six total measures (including % Poor and % Good) will be examined collectively to arrive at the best investment solution. These measures will help us make better long-term decisions and aid in the proper use of pavement preservation techniques. MnDOT needs to encourage innovation by including all types of fixes - both tested and relatively new - in the menu of potential types of fixes. There are a number of new ideas that are underutilized that could be used to

3 improve system performance. This investment philosophy will also be an opportunity for Districts to share success stories about their experiences with new techniques. Required Performance Measures Target measures for % Poor and % Good for each system - Interstate, other NHS and non-nhs - will continue to be used. They are based on the Ride Quality Index (RQI) - MnDOT s ride, or smoothness, index. It uses a zero to five rating scale, rounded to the nearest tenth. The higher the RQI, the smoother the road is. The RQI is intended to represent the rating that a typical road user would give to the pavement s smoothness as felt while driving the vehicle. Most new construction projects have an initial RQI of about 4.2 to 4.3. Pavements are normally designed for a terminal, or end of life, RQI value of 2.5. System Health Indicator Measures As the name implies, the following measures will be used to determine the overall health of the system. They help indicate if investments made are keeping up with the deterioration of the system and if sufficient resources are being set aside for preventive maintenance activities. Each of these measures is not mature enough to set rigid targets, however they do show in a simple way what direction the performance of the system is headed. All these measures are based in our RQI, or ride measure. Remaining Service Life The Remaining Service Life (RSL) is an estimate, in years, until the RQI, or ride measure will reach a value of 2.5, which is generally considered the end of a pavement s design life. Most pavements will need some type of major rehabilitation when the RQI has reached this value. MnDOT has calculated this measure for several years but has not used it formally in the decision making process. Remaining Service Life gives a good indication of projected pavement needs over a period of about 30 years and a good predictor of potential waves in the program during that period.

4 Asset Sustainability Ratio The Asset Sustainability Ratio, used by the Washington State DOT, measures the annual sustainability of investments in pavement asset protection. For a single year it measures how well MnDOT s pavement replenishment is keeping up with pavement wear. The annual consumption for MnDOT pavements is ~14,000 roadway-mile years. Annual replenishment is calculated as a summation of average life added per rehabilitation activity performed. In other words a 10 mile long overlay that is estimated to last 15 years would add 150 roadway- mile-years to replenishment side. The long term effects of the Asset Sustainability Ratio are evident in the Remaining Service Life calculation. Asset Value The Asset Value measure calculates the total current value of the pavement system. We currently use a very basic straight line depreciation model with $0 value at RQI =2.5 or 0 years RSL, and 25 years RSL is valued at $1,000,000 per roadway mile. This measure can be used to determine if we have under or over invested in pavements. Pavement Preservation Treatments Completed MnDOT has a history of developing and implementing the use of innovative pavement preservation techniques. Our recent manual at tion%20manual% pdf does a great job of describing the proper use of each treatment type. This measure is intend to encourage the use of these treatments on all our systems. The measure will compare the recommended treatment schedule to what is actually placed on the roadway during its lifetime. The measure will be expressed as a percentage of treatments completed on the planned construction project during the STIP years.

5 Investment Process MnDOT needs to optimize our investment at the network level. The Districts will use the Pavement Investment Guide software to run a variety of investment scenarios. Statewide pavement performance goals will continue to be set by the current MnDOT process. The key elements of the process are: Strategy - The condition of the road system for each District varies. These differences will require unique investment strategies for each District. It is expected that the percentages of long-term, medium term and pavement preservation treatments will vary to reach the optimum solution. The Districts will need to consider the following questions as they develop their strategy. 1. Where are you now? Examine the current condition of the three systems using all the measures described above with an emphasis on RSL histograms for the CHIP years. 2. Where do you want to go? Based on the current condition, funding limitations, and obligations, where can you expect to be in the STIP and CHIP time frames? However, even four and ten years can be too short to properly program pavement investment. In this question, Districts have the opportunity to look at long-term solutions to their performance goals. In other words, Districts may not be able to meet performance targets in the short term, but their selected strategy will be successful over an extended period. 3. What will success look like? Given the variability of funding this will be a difficult question to answer. Each District needs to review the outcomes illustrated by the measures and determine if use of the funding is optimized. The final result may vary from system improvement, to maintenance of existing condition, or to a slower rate of decline. 4. What innovative fixes have been used? We must encourage creativity and innovation by including all types of fixes. We have number of new fixes available and will have more in the future. Districts need to evaluate how they can fit into the program and what additional resources they may need to take advantage of these opportunities. There are associated risks with new technologies that must be understood before making a large investment. The Office of Materials and Road Research will provide the necessary guidance to help Districts make a more informed decision to minimize risk. Reporting Process An important part of this process is information sharing. All of MnDOT will be learning as we use this new method of investing. Some of the keys to success are: 1. Support and guidance from Central Office and District leadership - Leadership must provide the resources and consistent guidance to make this effort successful. They must also hold themselves and the Districts accountable throughout the process. 2. Best practices - We need to share results with each other to improve the process. The guide must meet the needs of the Districts to meet our ultimate goals. Continuous feedback to improve the process will occur at formal meetings like the Materials Engineers Organization and separate targeted meetings

6 3. Statewide meetings - Districts will report on their goals, investment strategy, and results at a statewide meeting. Districts will report on the following items for each system, Interstate, other NHS and Non NHS: A. General approach What are your current conditions and what are your goals, long and short term? B. How did you use the System Health Indicator Measures - RSL, asset value, Asset sustainability ratio and Pavement Preservation? C. Mix of fixes strategy What were your final percentages in each category and why did you come to that conclusion? D. Performance Measures What are your final results, year-by-year for the STIP and CHIP? Conclusion This process will help MnDOT make more informed and better decisions on how we invest in our pavements. The new measures will require us to take a longer-term look at our investments and lead to enhanced discussions on what funding should go to pavements versus our other transportation infrastructure. In addition, Districts will be in a better position to articulate their needs and show that they are spending their funds at an optimum level. Finally, MnDOT will be able to implement the latest pavement rehabilitation techniques at a faster rate by openly sharing pavement life-enhancing benefits in a statewide forum that will span across District boundaries.