The Göta älv-bridge is a welded steel bridge which is located in Gothenburg, it connects the inner city of Gothenburg with the island Hisingen. Cracks was discovered in the steel in 1999-2000 which started an investigation of the bridge to clearify the condition of the bridge. The conclusion was a monitoring system based on laser light sent through an optical fiber. This report describes the bridge, the damages, the monitoring system and the traffic on the bridge. Stefan Pup, at Vectura Borlänge was my supervisor during this work. In my investigation the costs of the monitoring system and the costs of closing the bridge is compared and evaluated. The biggest investigating part is the costs of closing the bridge. The results of my investigations is that closing the Göta älv-bridge would cost 1 107 300 SEK / day. The monitoring system has a cost based on actual costs til today, and forecasts until 2020 when a new bridge is expected to be in place, ending up at 41 144 086 SEK. To close the bridge would cost a lot of money. The monitoring system pays back in about a month with my calculations. That is a quite short time in comparison with the 15 years that the bridge has this monitoring system.