Hi there: We will be arriving Paris at St Lazare and departing from Nord on a Thalys train (will have pre-purchased tickets) - planning on taking either the Metro or taxi in between. How much time should we plan between the arrival of one train and departure of the Thalys train? We are 2 young adults able to move quickly, but will have bags in tow. Thanks for the help!
Take a look at this web page: http://www.seat61.com/Paris-metro.htm#How to cross Paris by metro According to the official Paris transport page ratp.fr
it's 7 minute walk from the Gare St-Lazare (SNCF) station, then a 4 minute ride on the RER E train, then a 6 minute walk to the Gare du Nord (without bags in tow :-). see the web page below (in French) http://www.ratp.fr/itineraires/fr/ratp/resultat-detaille/show/0/start/Gare+St-Lazare+%28SNCF%29%2C+Paris/end/Gare+Du+Nord+%28RER%29%2C+Paris/is_date_start/1/date/2011-07-11/time/21%3A50%3A00/mode/ferretram/route_type/minimum_de_changement RER is the suburban metro service. The taxi ride would be pretty short, but there could be a line waiting for taxis . . .
I've missed a train because of a Metro breakdown, and nearly missed a train from Montparnasse Station to Gare d'Est because of Taxi lines/crappy taxi driver. It's not worth the stress if you have the opportunity to give yourself plenty of time, so take the time that it "should" take given any reasonable estimate then double it.
To be more specific, is 1hr15min sufficient, or would 1hr45min be a better choice?
If you use the metro it will take thirty minutes, with one line change enroute. I'd just hop on bus #26 which connects the two stations and be there in less than fifteen minutes. It's only about a mile and a half. You can walk it in thirty minutes if the world explodes. You have more than enough time.