I have a .shp file (downloaded by googling USGS maps + census data + tiger ), loaded the file in QGIS. It contain various road lines in a city. In the attribute table it is showing only few properties ObjectId, LinerID, FullName, MTFCC. I am trying to retrieve the other information like length of road, width etc. But I not aware where I can get that information in QGIS.
If your crs is in a UTM projection, you can calculate the length of your line by using $length in the field calculator expression. You can't calculate the width of lines, only polygons, unless it is already stored in the attribute table.