How to take the RER from the Gare Du Nord to Gare De Lyon

If you want to opt to make the transfer between the Gare Du Nord and the Gare De Lyon by public transport, taking the RER train is the best option.

The four positives are:
(1) It’s comparatively fast - it’s a two station hop on Ligne D (Sud) - the green line, so you can be the concourse at Gare De Lyon, within 25 mins of entering the RER station at the Gare Du Nord.
(2)The line D platforms at the Gare Du Nord and Gare De Lyon stations have both been brightened up; and numerous staff can usually be found on the platforms at Gare Du Nord, so the station has lost much of what had been a somewhat intimidating atmosphere.
(3) It's cheap, a single central zone metro ticket can also be used on the RER.
(4) It's generally reliable, you won’t have to wait more than 12 minutes for a train and delays are very rare.

Not so great:

• The air-conditioning on the RER trains can be temperamental, so on a hot day, particularly if you are managing heavy luggage, it can be a tad uncomfortable
• Also the end-to-end the journey can be more confusing than you might imagine, hence the info below.

The RER Line D (Sud), which is the green line, provides the direct public transport link across central Paris between the Gare Du Nord and the Gare De Lyon - on this line the RER trains are double-decked local trains.

The transfer from being on the Hall 1 concourse at the Gare Du Nord, having arrived by Eurostar or InOui trains, to being on the concourse awaiting departure at the Gare De Lyon, will take a minimum of 20 mins.

However, these factors can increase that time to a more typical 35 to 45mins:

• If your seats are towards the rear of a train on arrival at the Gare Du Nord, it can take 5 mins to be on the concourse and heading for the RER trains - which are on the opposite side of the station from Eurostar arrivals.
• The need to buy a ticket for the RER transfer, as it won't be included in the ticket which covers the trains to and from Paris - See below on how to avoid being in a long line for a ticket machine.
• There can be gaps of up to 12 mins between the departures of the line D trains - If you're against the clock and need to avoid a longer wait for an RER line D Sud train, but a line B Sud train is about to depart from the opposite platform - take it and make the cross-platform transfer at the next stop, Chatelet Les Halles, into a Line A train on to the Gare De Lyon.

The access from the Eurostar arrivals to the main concourse at Gare Du Nord is all on one level; the exits from the voies (platforms/tracks) will be steps away from the front of the trains.
When you reach the concourse turn to the left.
Though what you won’t see anywhere at the Gare Du Nord are ‘this way to the Gare De Lyon’ signs.

There are multiple access points to the RER trains across the back of the concourse at the Gare Du Nord.

However, the main entrance to the RER station is towards the far left of the concourse (pictured below)

The spacious atrium makes the route to take towards the RER trains comparatively obvious - hence it being SMTJ's preferred route to the RER.

You will come to an escalators which leads down into the RER concourse; This image below has been taken from the top of this escalator.
There is a lift /elevator available, but it is further over to the left, by the entrance to the Hall 3 B

When you reach the foot of the escalator, walk ahead of you into the RER station, the ticket machines and counters for the line D (and B) trains will then be over to the left; the access down to the trains is on the other side of the ticket machines.

Your end-2-end train journey ticket will not include the RER, so you will need to buy the Metro-Train-RER ticket, which costs €2.50.

Worth knowing is that Paris has pretty much transitioned to a Pay As You Go system for its public transport network, based on navigo cards.
There are two core methods of using navigo:
1 - A plastic card which is automatically issued by ticket machines and ticket counters when you inform the machines or staff, that you don't already have a card - the cost of the card is €2.
2. Downloading the navigo app to a mobile device.

The big plus of bothering to download the mobile app, is that you can then use mobile banking to pay for tickets to be added to it, so can then avoid the ticket machines and counters!

The staffed ticket counter in the RER station is only open at certain times of the day, so to mitigate against this, multi-lingual staff can be assigned to each ticket machine, to ensure the correct ticket is purchased.
However, queues of more than 10 people per ticket machine can be typical

The excellent parisbytrain website has all the info you will need about metro tickets.

From the RER concourse follow the signs for ‘Ligne D (Sud)
It’s important to use the ‘Ligne D (Sud)’ ticket gates as there are separate/different ticket barriers for trains heading in the opposite direction (Nord).
If you have luggage, use the lift/elevator on the other side of the ticket gates - it goes directly down to the platforms/tracks.

The RER station at the Gare Du Nord is now housed within a smart mall area - so when you take the initial escalator down, you will find yourself in this mall.
The second set of escalators, which you will see directly ahead of you, typically lead upwards for the benefit of arriving travellers, so you will need to walk around behind them, to the next set of escalators.
They will be be marked RER Line B Sud and RER line D Sud and they will take you down to the train - the train will depart from Voie (platform) 44.

The platform is shared by Line B (Sud) and Line D (Sud) trains, the line B trains use the track towards the wall (voie 42), while the line D trains use the track towards the middle, facing the northbound trains (voie 44).
All Line D trains heading south from the voie 44 will call at the Gare De Lyon which is two station calls from Gare Du Nord, so don't worry about the final destination of the train.

Though you can check the electronic departure screens on the voie/platform to double check that you will be boarding a Line D train; or confirm it with the SNCF staff that are usually on the platform.

The train will be double deck, but don’t bother with finding a seat, as the travel time is only around 7–8 mins.
It’s easier to wait in the fairly large area just inside by the doors, though allow room for people to alight and board at the intermediate station, Châtelet–Les Halles.

At Gare De Lyon there are escalators and lifts / elevators) up to the level above which houses the exits from the RER.

Though the locations of the lifts / elevators can inevitably be less obvious, so you can use the signs to find them if need be.

You will ascend up to the RER concourse - note that it's also used by people heading the opposite direction to board an RER train.
It's in effect a large white space, so you need to follow the signs which either point the way to the 'Grande Lignes (mainline trains), or the Halls 1, 2 and 3 -These are the departure halls that the Grande Lignes trains / long-distance trains will be leaving from.

Below is an example of the signage that can be found on this RER concourse.

In the middle of the image is a column and on it are multiple direction signs - the one at the top is informing travellers that if you head in this direction, you will be going towards the Grande Lignes trains.

This sign is above the exit gates from the RER station, which lead to the route towards the onward trains.
At this stage there is no need to be aware of which voie (platform / track) or departure hall that your train will be leaving from, the route from here will take you to any onward departure.

When you passed through the gates from the RER station, you will come to the lobby area which leads to the parts of the Gare De Lyon that have the access to the Grande Lignes / mainline trains.

Hall 3 at the Gare De Lyon has a dual function:

• it gives access to onward trains which will be departing from voies (platforms / tracks) E to N.
• it's a passage way which leads to Hall 2, which is where the other onward trains departing from voies (platforms / tracks) 5 - 23
  So when you come to the escalators which lead up into Hall 3, you can ascend by them, regardless of which train you will be taking.
  

When you have ascended into Hall 3 you can use the blue 'Départs Grande Lignes' screens to check either;

• which voie (platform / track) you need to head to board your onward train - You'll likely see the details of the specific voie (platform / track) if your train will be departing within 15 - 20 minutes, or
• which of the departure halls in which you should wait for the departure details of your train to be confirmed.
  Note that for some departures you can remain in Hall 3, there are entrances to each of the voies E to N on the right-hand side.

On the above example, if you happened to be taking:

• the 13:16 train to Montargis - you could proceed directly to voie N
• the 13:46 train to Monteraux - you can wait in Hall 3 for the specific voie that it will be leaving from, to appear on the screen
• the 13:54 train to Lyon Perrache - you should head to Hall 2 to await its departure details, it will be leaving from voies 5 to 23
• the 14:10 train to Nice - you can wait in Hall 3 for the specific voie that it will be leaving from, it will be leaving from voies E to N.
• the 14:14 train to Lyon Perrache - you should head to Hall 1 to await its departure details, the Hall 1 can be accessed from Hall 2
• the 14:18 train to Lausanne and the 14:22 train to Basel - you should head to Hall 2 to await their departure details

Departing from Hall 2:

Towards the far end of Hall 3 you'll find the access up to Hall 2.
The most obvious route is the sloped pathway beside a moving walkway.
However, if you don't want to drag heavy luggage up the slope and the moving walkway is either unavailable or heading downwards, beyond the slope you'll come to some escalators - at least one of which should be heading upwards.

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