The tunnel consists of segments that are 90 m long. The total length of the First Coen Tunnel is 1283 m, of which 587 m is fully covered. The tunnel consists of two tubes separated by an intermediate corridor. The corridor can be used as an escape route in the event of an emergency. The west tunnel is used for traffic from Zaandam to The Hague, while the east tube is used for traffic travelling in the opposite direction.
Inspection on location was carried out over two nights when the tunnel tubes were closed for maintenance. Cylinders were drilled at different locations in the tunnel, taken from the deck and out of the wall. At the same time, measurements were taken to determine the concrete cover of the reinforcement in the vicinity of the drilling locations. The tunnels were also visually inspected to determine if there was any frost damage.