Definition of "concurrently"

For the next four years Mr. Johnson continued building 2-4-0 express passenger engines, thus continuing the Kirtley practice, but from 1882 onwards he built all his express engines with the 4-4-0 or the 4-2-2 wheel arrangement, the two types being put in service concurrently between the years of 1887 and 1900.

1934 February, H. C. Casserley, “A Veteran Midland Locomotive”, in Railway Magazine, page 86

Concurrently with the St. Pancras-Bedford service, diesel trains have now taken over that between Kentish Town and Barking, on an even-interval basis at half-hourly intervals.

1960 February, “The dieselised St. Pancras suburban service”, in Trains Illustrated, page 95