Yes, TRANSITS is a Scrabble word!

Letter values in Scrabble US: T 1, R 1, A 1, N 1, S 1, I 1, T 1, S 1.

Is it a valid word?

TRANSITS is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

a surveying instrument for measuring horizontal and vertical angles, consisting of a small telescope mounted on a tripod
a facility consisting of the means and equipment necessary for the movement of passengers or goods
a journey usually by ship

make a passage or journey from one place to another
pass across (a sign or house of the zodiac) or pass across (the disk of a celestial body or the meridian of a place)
revolve (the telescope of a surveying transit) about its horizontal transverse axis in order to reverse its direction
cause or enable to pass through

Also: transportation system, pass through, move through, pass across, pass over.