If you were leaving from the center of Paris (Les Halles) on a Wednesday morning, this is what your itinerary would look like. Google maps indicates 24 minutes, which is optimistic. Outbound traffic is usually lighter than inbound, but please allow a solid 45 minutes to get to the university. A cab ride from the center of Paris to the university can range from 30 to 50€, depending on the service you are using. Distance from Les Halles to Champs sur Marne is ca 23 km.
For public transport details, see below:
FYI: from the center of Paris (Châtelet – Les Halles) allow 45 minutes (usual 10-minute wait, 25-minute train ride from Châtelet-Les Halles to Noisy Champs, 10-15-minute walk from RER train station to university Copernic building).
To come to the Université Gustave Eiffel, please take the RER A4 line to the station “Noisy Champs.”
PURCHASING TICKETS OR NAVIGO PASS
You have two options:
 RER tickets. You can purchase a special ticket from Paris – Noisy Champs (you can do so in any metro or RER station). You will need a return ticket (the machine will give you two tickets – it does not matter if they are inscribed Paris – Noisy Champs, they work both ways). Cost as of March 2022 is 4,45€ one way. If you are not staying in Paris, but in the suburbs, you may want to purchase a special ticket from the suburb where you are staying to Noisy-Champs. For instance, if you are staying in Antony (south of Paris), you will want a ticket from Antony to Noisy-Champs (which is more expensive than a Paris–Noisy-Champs ticket). The RATP has a point to point simulator that allows you to calculate what ticket you need: https://www.ratp.fr/en/titres-et-tarifs/ile-de-france-idf-point-point-ticketsPlease hold on to your ticket once you enter the métro / RER station (do not discard it), as you will need it to exit the “Noisy-Champs” station.
 If you are staying several days in Paris, you may wish to buy an all-zone weekly pass (Noisy Champs is in Zone 4 as shown on the map line above) which will allow you to use the RATP network (métro, bus, RER) without restrictions. This will also allow you to get from and to airport Charles de Gaulle. Cost as of March 22 for an all-zone weekly pass is 22.80€. Navigos can be purchased from the RATP booths or machines in métro & RER train stations. Detailed information here.
WHERE TO TAKE THE RER TRAIN, IN WHAT DIRECTION?
In Paris you can board the RER A at the following train stations: Charles de Gaulle Etoile, Auber, Châtelet Les Halles, Gare de Lyon, Nation. You will want to take an East-bound RER A going towards Torcy / Marne-la-Vallée Chessy. Known as the A4 line, it’s the superior branch of the Eastern part of the line. Its terminus is Eurodisney.
When coming from Paris, please board one of the front cars of the train: when you get off at Noisy Champs, you will be close to the exit leading to the University. Walk to the escalators. As you go up the escalators from the platform, take the exit located on your right, exit #3 “bd Newton.”