A total of approximately 10,000 square meters of breaker-crushed limestone and 6,000 square meters of excavated soil were removed in the course of the construction of the tunnel, which includes a 150-meter enclosed area and 125-meter-long ramp.

1,000 square meters of concrete was poured or assembled, to which the tramways together with their supporting structure will add another approximately 700 cubic meters of volume.

According to Tallinn City Transport board director Enno Tamm, the greatest challenge of constructing the airport extension of the tram line was the need to route it under the existing railway and Suur-Sõjamäe Street.

"We previously lacked experience in Estonia with planning and contructing a bi-level railway and tramway crossing without interrupting rail traffic," Tamm explained. "The builders managed the task brilliantly, which once again confirms that the goal to begin tram service to the airport in September is doable."

Construction of the airport extension of the number 4 tram line, which began last August and the bulk of which has been completed already, will cost a total of €12.5 million.