I'm looking for examples of efficient rail construction. On Pedestrian Observations, can you find the construction cost per kilometer for the Barcelona rail tunnel, which is noted for its low cost? Please state the approximate cost per kilometer as mentioned in the article.
Navigate to 'pedestrianobservations.com' Click on the 'Construction Costs' link in the navigation menu. On the 'Construction Costs' page, locate and click the 'Quick Note: Barcelona Rail Tunnel' link. Extract the approximate construction cost per kilometer for the Barcelona rail tunnel from the article. State the extracted construction cost.
Successfully navigate to the 'Construction Costs' page. Successfully navigate to the 'Quick Note: Barcelona Rail Tunnel' article. State the construction cost per kilometer for the Barcelona rail tunnel as approximately $40 million.