how much speed can a digital ho-scale modeltrain attain?(km/h or m/s))?

Question

And another question: can one buy the TGV in ho-scale?

Answer 1

Yes, you can buy the TGV in HO-scale (and N-scale).... I'll hunt up the link(s). There are also models of the Aceala.

UPDATE: Kato used to sell the TGV : http://www.discounttrainsonline.com/Kato-TGV-6-CAR-SET-ORNGEGRY-/item381-10198.html in HO... now they only have it in N SCALE !!

Now regarding SPEED... most HO railroads go up to about 35-40 TRUE MPH... but that can equal a much higher SCALE speed. Now let me convert that :P
Over 3 feet:
5mph (8.04 Km/h) - 36 seconds
10 (16.09) - 12 sec
25 (40.23 - 7 sec
60 (96.56)- 3 sec
90 (144.84) - 2 sec

Below is a link to operating model trains at SCALE speed.