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NEWS (Previous News Items)

  • To identify pavement treatment surfaces that are more acceptable to California’s increasing number of bicyclists as well as safe for motorists, the UCPRC undertook and recently completed the second part of a Caltrans-sponsored study into roughness and surface textures that could satisfy both sets of road users. A report on the study is now available. It contains a set of recommended guidelines that can be used to select pavement surface treatments for both urban and rural roads that maximize bicycle ride quality based on surface texture, combined with the effects of road roughness. This multi-faceted study built on the earlier study by including a wider range of bicycle types and riders, and considering urban preservation treatments and city streets as well as treatments used on state highways and county roads. The recommendations in the study are based on user surveys as well as investigation of the effects of preservation treatment aggregate gradations on surface texture and the mechanistic responses of bicycles to pavement macrotexture and roughness.
  • Three new technical memos are now available that document Caltrans-sponsored UCPRC research on projects whose aim is the development of HMA performance-based specifications for long-life pavements. The memos provide the study’s results and describe how Caltrans and the UCPRC collaborated to finalize the mix designs, perform laboratory mix testing, and establish performance criteria for two long-life pavement projects in Caltrans District 2 (one north of the city of Red Bluff and another north of the city of Weed) and one in District 4 (on Interstate 80 in Solano County). Caltrans put the resulting data to use by making it available to contractors bidding to construct the projects and by having its staff pavement designers use it with CalME flexible pavement design methodology. Now that the projects are in place, Caltrans has continued the follow up performance monitoring included in the memos’ recommendations. Posted 11/8/2016.
  • Throughout the summer, the UCPRC has continued sampling pavement materials from asphalt plants around California to gather data for the Standard Materials Library in development for Caltrans and for use in the pavement design software CalME. This sampling work and the research that will build on it have been enabled by industry partners, whose facilities include equipment like the new asphalt sampler and splitter in use at plants in Orland and San Diego. This device minimizes the impact of sampling asphalt materials during production. Posted 7/19/2016.
  • Pavement structural response, macrotexture, and roughness all affect vehicle fuel consumption, but how great the effect of structural response is has not been fully examined yet. A new UCPRC report provides insights based on calculations made with data from measurements on 17 asphalt-surfaced California pavements, including flexible, composite and semi-rigid structures. Three types of models were use to simulate annual excess fuel consumption due to structural response (EFCS) for a factorial of vehicles, traffics flows, speed distributions, and climate regions, and these results were compared with increased fuel consumption caused by roughness and macrotexture. Initial recommendations from the study include adding models for concrete pavements, considering multiple layers in the asphalt, and checking the effects of full dynamic pavement modeling. The next step in the project is field calibration of the models. Posted 6/1/2016.
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Fall 2016 UCPRC Activities


Candidate for fully permeable shoulder retrofit validation site

Effect of Pavement Structural Response on Vehicle Fuel Consumption and Emissions: Field Calibration of Models. Pavements have an influence on the fuel mileage of cars and trucks. For individual cars and trucks this influence is small (generally less than about 3 percent change in fuel mileage compared to a “perfect” pavement) relative to the fuel mileage effects of stop-and-start and “lead foot” driving, the air resistance on a vehicle traveling over a freeway speed limit, and underinflated tires. But since the pavement effect applies to every vehicle on the road its cumulative effect is magnified.

The pavement characteristics considered to affect fuel economy are roughness (bumpiness), texture (the stones sticking out of the surface), and the structural response (bending under load) of the pavement itself. To date, models that have had some field calibration only exist for the effects of roughness and texture.

During the summer of 2016, in the second phase of a Caltrans-sponsored study, the UCPRC investigated the effects of pavement structural response (the bending under load phenomenon), along with verifying models for roughness and texture.

In Phase 1 of this study, researchers at Michigan State University, the Massachusetts Institute of Technology, and Oregon State University developed models for the mechanics of pavement structural response on vehicle fuel consumption. UCPRC researchers then used the models—along with existing models of roughness and texture—to run simulations of annual fuel economy in different climate regions, with urban and rural traffic speed (congested, uncongested) and traffic flow (vehicle types) conditions. (A report on Phase 1 is available here.)

The objectives of Phase 2 of the study are to measure field vehicle fuel consumption on different pavement types in both winter and summer, and to finalize the development of calibrated and validated models for vehicle energy consumption due to pavement structural response that can be used in pavement management and design.

The Phase 2 study began in mid-2015 with the identification and field measurement response of 21 test sections across northern and central California, including a range of pavement structure types. The pavement structures are being characterized for their structural characteristics (material types, thicknesses and stiffnesses), and surface roughness and texture. A mix of vehicles types is being used to gather fuel economy measurements: a five-axle, semi-trailer tractor; a 1.5 ton single-axle, dual-tire diesel truck; an SUV; a gasoline-powered car; and a diesel car. All have been fitted with new tires that were broken in and then kept in cold storage when they were not in use. On-board diagnostic systems in each vehicle record air flow, fuel injection, vehicle speed, and fuel consumption. In addition, temperature and wind conditions are monitored during testing. To ensure consistency, the same vehicles and drivers are used during testing, and to get statistically meaningful results a number of runs are made on each section.

The current round of testing is expected to be complete by the end of September, and the entire project is scheduled to end in early 2017.

Important Note for Caltrans Users: Prior to scheduling pavement preservation (preventive maintenance or CAPM) or roadway rehabilitation work on flexible pavement highway sections, the District Materials Engineer and/or the Project Manager should review this spreadsheet to ensure that the proposed project does not include sections active in the “Quieter Pavement Research” (QPR) testing program. If the proposed project is within a QPR test section, please contact Linus Motumah of the Caltrans Office of Pavement Design before scheduling the work.

To view maps that show where the sections are located, click the following link: (or copy-and-paste it into a new browser window for a slightly larger view).

For more information, contact John Harvey of the UCPRC or Linus Motumah.