One thing that helps a lot with the Nuvi is the traffic receiver. I don't know how it handles seasonal road closures but for rerouting around traffic in metro areas like Los Angeles and warning about delays due to accidents and construction, it's great.

I may contact Garmin to see how it is supposed to deal with seasonal closures. Those may be outside the high traffic areas covered by the traffic receiver so they may not show up as closed. Hmmm