The biggest problem with a direct import is that major Arkansas roads have seen hundreds of hours of labor invested in creating the routing network, improving alignment, and tagging attributes. Minor roads have been manually improved in selected areas. Any use of the improved state data must preserve the existing work.
One answer is to selectively use the "Replace Geometry" tool from JOSM's [Utils Plugin 2][1] while copying road by road from the official state data loaded into another layer. However, this does not preserve the endpoint connectivity. The official state data tagging would need to be reviewed for proper conversion from shapefiles to conform to OSM standards - for example to remove abbreviations and proper use of upper and lower case.
The problem of how to ease use of updated road network data is quite advanced, and exists at varying levels in many counties across the US. The best solution would be a dedicated editor plugin that allows updating the road geometries one by one while preserving the connectivity, existing tags, and bridges. Some of these updates would require manual intervention to correct the result and cannot be applied on a mass scale.
[1]: http://josm.openstreetmap.de/wiki/Help/Plugin/UtilsPlugin2
