The Zaragoza North Beltway borders the city to the West and North, crossing the River Ebro and the River Gállego, as a continuation of the A-2 motorway and incorporating other important roads: Z-40 South Beltway, A-68 highway, AP-68 highway, A-23 highway and again the Z-40 East Beltway. The scope of the contract includes construction site supervision for additional lanes, improvement to junctions and a 18 km section between K.P. 313.00 and 331.00. One of the most demanding conditioning factors was that traffic could not be interrupted during execution of the work. Key structures include 9 junctions, 32 underpasses, 10 overpasses, one 520 m bridge over the River Gállego and a 240 m bridge over the River Ebro. Another key factor was the variety of services of all types affected: high, medium and low voltage power lines, gas mains, telephone lines from different companies and relocation of irrigation ditches and other impacts on individuals.