The traffic in Paris is notoriously bad at any time of year so bringing a car is not a good idea. The Peripherique - Paris' Ring Road - is often clogged, but tends to move albeit fitfully. However with the Periperhique gridlock is often the case.
Two ways of avoiding this are available - the Velib Scheme of city-wide bicycle hire (see picture) which is proving very popular. Once subscribed you can pick up a bike at any one of numerous self-service "Stations" and return it to any other for a modest charge. There are however reportedly some problems around Sacre Coeur and Montmartre which are on a hill overlooking the city - everyone seems to pick up a bike at the top of the hill to ride down, but few choose to ride up the hill resulting in a lack of bikes at the top,
The other traffic-free option is the BATOBUS, a river bus service which runs from the Eiffel Tower down to the Jardin des Plantes calling at the Musee d'Orsay, St Germain des Pres, Notre Dame, Hotel de Ville, Louvre and Champs-Elysees - just get on and off where you choose for €12 per day (or €14 for 2 days) - and get some great views of the city into the bargain.
