In 1999, the Transport Unit of the World Bank Group (WBG) first developed the Road Costs Knowledge System (ROCKS) , an empirical study of road-related projects completed by the WBG. The study was designed to obtain average and range of unit costs based on historical data that could improve the reliability of new cost estimates and reduce the risks generated by cost overruns. The Transport Unit last updated the study in 2008. Key features of the original ROCKS database include:
- a systematic classification of the road works in categories of work type (e.g. new road construction, resurfacing, routine maintenance, widening, etc.);
- the actual and estimated unit costs of the road works defined as costs per km and per m2;
- the primary details of each project (e.g. country, date, currency, pavement width, terrain type, etc.);
- the conversion of all costs to a single currency (US$). The original ROCKS contained more than 3,000 records covering 89 low and middle-income countries.
Over the last year, the Doing Business team updated the ROCKS database by adding more recent data. The team analyzed all WBG-financed projects with a road component that were completed between the years 2000 and 2017, and extracted information on project cost, length and duration from Project Appraisal Documents, Contracts and Completion Reports. This update led to the inclusion of more than 150 new projects in over 70 countries. To complement the analysis, road-related projects financed by the African and Asian Development Banks were also included.