I have been learning about the TIGER and the National Map datasets for mapping roads in the United States.
One limitation is that as far as I can see there is no data on the number of lanes. The main available attribute seems to be "road class" which is things like "Freeway", "Collector", "Local Road" etc, which does not really indicate the number of lanes the road has. For my purpose I am mostly interested in knowing the number of lanes and whether it is a divided highway or not (ie has a central barrier), or if it has a median, like most interstates do. Is there any way to get this information?