RER from CDG to Gare du Lyon

B to A in the same direction (heading south and west) should be a simple cross platform change at Les Halles. Map here

https://community.ricksteves.com/travel-forum/france/cdg-to-gare-lyon

http://www.aeroportsdeparis.fr/ADP/en-GB/Passagers/Access-maps-car-parks/Paris-CDG/Access/public-transport/
(Les cars is the Air France bus/coach service. Line 4: Gare Montparnasse or Gare de Lyon - Aéroport Paris-Charles de Gaulle)

http://travel.state.gov/content/passports/english/country/france.html

Pickpockets are very active on the rail link (RER B) from Charles de
Gaulle Airport to the city center. Travelers may want to consider
using a shuttle service or one of the express buses to central Paris
rather than the RER.

Hi,

With public transportation you can take the RER and the bus. Take RER B from CDG to Gard du Nord, then transfer to Bus # 65 (in front of the Chinese restaurant 'Le Jumbo') to Gare de Lyon. I'd take the bus when w/o luggage. Or, at Gard du Nord/Magenta you can take the RER D to Gare de Lyon, if you have luggage. Better still is the shuittle as suggested above.

Magenta is the RER E and it goes to St Lazare. I don't recall if it is a cross platform transfer at Nord between the B and D, but it likely is.

Another recommendation, if you have any luggage at all, to take the Air France bus direct from CDG to Gare de Lyon. Much more comfortable and you diminish your risk of being robbed substantially (basically you eliminate the risk).

As a Parisian I am used to the second way = RER line B from CDG airport to Chatelet-Les Halles, then change for RER line A ( direction Boissy St Léger - Marne la Vallée ) and stop at Gare de Lyon ( we don't use line D that much, actually ). The main interest in keeping the RER line instead of changing for a Metro line is the gain of time since there are fewer stops ( actually coming from Les Halles the next stop is Gare de Lyon ). Even you have to change platform, there are escalators.

To be on Friday in the morning don't mean more than any other day except SUN : rush hrs are always busy... I would give roughly 50 mn transptt time from airport station to train station ; allow 1 hr to be on the safe side including a 5-10 mn for the connection at Les Halles..

The fact of being carrying bags as a tourist a potential target for thieves is another issue : I do understand that some prefer to take the bus, but hey, hundreds of tourists go that way by RER and never have a pbm... You need to be awake and watch out, that's all.