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Welcome to Chris Bennett's and Lis Pedersen's web site. If you are looking for information Chris' current work on affordable housing, please visit www.mygbhousing.info. The video below tells the background to Chris' project.


2014 - USA - Impact of Pavement Roughness on Vehicle Free-Flow Speed


2014 - USA - Impact of Pavement Roughness on Vehicle Free-Flow Speed

To investigate the impact of changes in pavement roughness on speed, this study developed a linear regression model to estimate free-flow speed on freeways in California. The explanatory variables include lane number, total number of lanes, day of the week, region (district), gasoline price, and pavement roughness as measured by the international roughness index (IRI). Data on the California freeway network from 2000 to 2011 were used to build the model. The results showed that pavement roughness has a very small effect on free-flow speed within the range of this study. For the IRI coverage in this study (90% of the records have an IRI of three m=km or lower and 90% of the records have an IRI change of two m=km or lower), a change of IRI of one m=km (63 in:=mi) results in a change of average free-flow speed of approximately 0.48–0.64 km=h (0.3–0.4 mph). This result indicated that making a rough segment of pavement smoother through application of a maintenance or rehabilitation treatment will not result in substantially faster vehicle operating speeds, and therefore the energy and emission reductions gained from the reduced rolling resistance will not be offset by increased fuel consumption from faster speeds. However, developing a good model to predict the free-flow speed was not fully successful. The southern California interstate freeway model yielded the best result with an adjusted R-squared of 0.72. For the rest of the regions in the state, the selected explanatory variables can only explain approximately half of the total variance, indicating there are still other variables with more substantial effects on free-flow speed that were not covered in this study

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Created Date: 26-09-2022
Last Updated Date: 21-02-2024


Chris in the NCT Race 

Chris has an adventurous spirit which generally involves cycling, running, or just being out there having a good time. Read his 'Race Reports' below. This is a link to his SPOT GPS tracker. If you are interested in his 'geeky' sport technical blog it is at www.tri-duffer.com. He also has stories of his life as 'An Overtravelled Engineer Working for the World Bank' at World Bank Traveller.


Race Reports


Document Library


  • Chris' published papers and reports are here.
  • His Technical Library  has a range of reports 
  • Golden Bay community projects are here.
  • The history of the ROMDAS company is here.
  • The 'Road to Good Health' HIV/AIDs Toolkit is here.


Technical Library

Chris and Lis

Chris and Lis

We are Lis Pedersen and Chris Bennett. We’ve been married over 30 years and each found our way to New Zealand in the early 1980s from Denmark and Canada respectively. Golden Bay has been our happy place for almost 20 years and we are now based in Pohara just above the beach, with our two cats Coco and Max. 




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