Always important to have licensed engineer and experienced contracting officer involved. Risk issues includes assessing construction materials, allowable practice limits, site, geology, soils, hydrology, watershed, etc. An experienced, licensed engineer, who is licensed, insured, bonded is not going to sign plans without consulting specialists needed, and work with contracting officer or specialist to ensure adequate specifications. As a certified professional hydrologist, I do have some concern that the risk and uncertainty of hydrology conditions are not always understood or assessed fully. And it is difficult for professionals and decision makers to design for long term using the 100 year flood, with the understanding that the flow estimates have a plus or minus confidence limit of 40% or more, and significant land use and other changes can occur to consider for long term sustainability. Considering highways and water conveyance structures, design and management must always consider the potential and risk of flows exceeding a design, so conditions and frequency of short term closures may be needed. Not all highways and roads are designed with same level of risk considered, so transportation planning and management of the highway and road system needed, and identifying added risks from floods or other calamities from the potential for dam failures, landslides, etc. For many construction projects, the requirement of a performance bond seems appropriate to protect the funding agency or community from loss due to negligent, poor or lack of performance. The US as well as many other countries have examples of contract specs for highway construction, so seeking examples for terrain involved would be helpful, but recognizing not all contracts and decisions view design and risk the same. And if you are designing a highway that is a public major urban evacuation route from calamity (hurricane, tsunam, earthquake, etc), the design specs may have to be upgraded in various ways.

Specifying codes and standards goes a long way. It provides not just the initial design parameters but also goes into long term maintenance. Specify the post-construction methods and codes in the contracts as well as the design codes and methods.