## 3 Results and Discussion
### Bibliometric Analysis of Research on Pavement Management (2000-2013)
#### Publication Distribution of Countries, Institutes and Authors  
The analysis of author's countries/territories was based on papers in which the address and affiliation of at least one author was provided. There were 16 papers without any author name (11) or address information (5), on Scopus. Therefore, the total number for distribution analysis of country publications was 711. Among all the publications with author address, 628 (88.3%) were single country publications, and 83 (11.7%) were international collaborative publications. Table 2 shows the top 20 countries ranked by the number of total publications with other information: the ranking and percentage of contribution according to single country or internationally collaborated papers, as well as first authors and corresponding authors. Some categories, like total \begin{table}
\begin{tabular}{c l c c} \hline \hline
**Ranking** & **Journal** & **Documents** & **Percentage (\%)** \\ \hline
1 & Geotechnical Special Publication & 17 & 2.3 \\ \hline
2 & Proceedings Annual Conference Canadian Society for Civil Engineering & 14 & 1.9 \\ \hline
3 & Proceedings of the 1 st Congress of the Transportation \& Development & 11 & 1.5 \\  & Institute of ASCE & & \\ \hline
4 & Proceedings International Conference on Applications of Advanced & 10 & 1.4 \\  & Technologies in Transportation Engineering & 9 & 1.2 \\ \hline
5 & Proceedings of the 2013 Airfield and Highway Pavement Conference & 9 & 1.2 \\ \hline
6 & Proceedings of SPIE the International Society for Optical Engineering & 7 & 1.0 \\ \hline
7 & Proceedings of the 2006 Airfield and Highway Pavement & 6 & 0.8 \\  & Specialty Conference & & \\ \hline
8 & 2010 Annual Conference and Exhibition of the Transportation & 6 & 0.8 \\  & Association of Canada & & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: The most important congresses and conference proceedings (with more than 5 documents). publications or countries, are non-exclusive, so it is possible that some documents can be classified in more than one country simultaneously, as consequence of international collaborations. Therefore, the sum of the number of documents in these categories is above the total number of documents, and a similar result can be found in percentages, with results above 100%. The existence of a reduced number of countries that dominate the publication of scientific documents was expected, as this pattern is very common in most scientific fields [51; 52; 53], including civil engineering [54; 55]. The top 10 countries in Table 2 produced more than 85% of the total number of documents. The analysis demonstrated that the United States was the most productive country, with more than 340 documents (48.9%) This leader country was followed by Canada (85 documents, 12.0%) and China (69 documents, 9.7%). These three countries had been previously identified among the top four contributors in the research fields related to civil engineering [54]. The contribution of different institutions was estimated by the institution of affiliation of at least one author of the published papers. The top 13 institutions, the only ones which produced more than 10 documents, were ranked by their number of publications (Table 3). Among these institutions, 8 were American, 2 Canadian, and one each from China, Portugal and Taiwan. These five countries occupied the top five positions in the ranking of most productive countries. The leading organization was University of Waterloo, with 25 publications, followed by Universidade de Coimbra with 22 documents. Moreover, among the top 13 institutions, two private companies could be identified (Applied Research Associates Inc. (Albuquerque, NM, USA) from the United States, with 14 documents, and Stantec Inc. (Edmonton, AB, Canada) from Canada, with 12 publications), as well as a public institution from the United States (California Department of Transportation with 11 documents).