Wash DC has 'interesting' topography and layout. Coming in from the Maryland side, it is almost all down hill... but traffic converges at just a few points. (many side streets have restrictions about direction during rush hours) so any sort of delay... accident or snow... is compounded. Leaving, the streets gradually branch as one gets further out, but a lot of it is UP hill. Add to this lots of bureaucrats and wealthy suburbanites who feel 'too important' to be hindered, plus taxi drivers from Pakistan, Ethopia...etc., whose idea of driving rules is a bit different, and who are not familiar with snow & ice... and you get a recipe for interesting commutes.
Maryland has many odd roads that were originally paths to mills, etc (I am not as familiar with Virginia's, but I know it has 'em too.) Snow & ice are not regular issues here, and when you add I-66, I-95, I-495 (the beltway) and several bridges, it makes the D.C. area one of the 2-3 worst driving areas in the country.