These trains are fast. They can travel at very high speeds.
These trains are fast. They can travel at very high speed.
Can I say "at very high speed" in that context? If it is possible, what’s the difference between two sentences?
[I can say the first version in my native language, but it’s very, very informal.]
Say Eurostar can travel at 179, 180 or 190 miles per hour. It can travel at very high speeds. Right now it goes 160mph, which is still a very high speed.
“High speed” for the general case is also fine.