Element Full Corridor Scheme (Costs £million) Managed Crossing Scheme (Costs £million) Cost Difference (Costs £million) Network Connections 441 214 227 ITS and Supervision 41 26 15 Main Crossing 613 455 157 Approach Viaducts 108 82 26 Sub Total exc. risk, optimism bias and VAT 1,204 777 427 Risk Allowance 160 95 65 Optimism Bias 499 178 321 Sub-total exc.