The phrase
"significant congestion" means there is a large amount of traffic or blockage causing delays or crowdedness.
Full definition
The 3,000 tickets issued to Cologne fans was in line with competition rules but it is clear many more visiting fans arrived,
causing significant congestion and disturbance outside the stadium before kick - off.
California's electric market will face a number of challenges this summer, the greatest of which is making up the loss of two nuclear units (San Onofre 2 & 3) in an area
of significant congestion on the electric system.
In the unlikely event that Bitcoin was implemented as an immediate method of payment, the Bitcoin Blockchain would probably suffer
from significant congestion and elevated transaction fees.