How bad is traffic from Tokyo to Narita in the early afternoon? Very specifically, if I want to take the limo bus from the Hotel Okura to Narita, so that we can arrive around 4pm for a 6pm flight, what time should we leave?

Traffic in Tokyo is notoriously bad, but you won't be travelling at the worst time. Best to inquire at the hotel directly when you book your seats on the bus. They will be able to tell you which bus to take in order to arrive in time. You can do this the day before your flight.

If your airline offers the check-in service at TCAT, you could go there 3 hours prior to your departure time. Best part of this is you can also complete the immigration process at TCAT while you wait for your bus. All you have to do at Narita is security checks.

tadaoji-san and richarddd-san,

Unfortunately, city check-in counters and immigration at TCAT are all closed now after 911.

Still, it would be better to catch a limo bus to Narita at TCAT, because TCAT is the most frequently serviced bus stop in Tokyo(about every 10 min.),
and buses can go directly to highway.

In fact, generally speaking, much of the travelling time of a limo bus is used during snailing the downtown Tokyo.

As KimJapan-san said, you should ask hotel staff before check-out.

I didn't know it!! I have not used TCAT for some years and always missed the conveniece since my airline (I stick to them for the FF program) stopped the check-in service at TCAT some years ago.

Now I don't have to grumble about it anymore. Thank you.