The construction industry encompasses building and engineering projects (e.g., highways and utility systems) including new work, additions, alterations, or maintenance and repairs. Major services include design, engineering, construction, project management and maintenance of buildings and structures. Production responsibilities for establishments in this sector are specified in contracts with the owners of construction projects (prime contracts) and contracts with other construction establishments (subcontracts). Commercial and heavy construction contractors focus on building nonresidential buildings (industrial, commercial, institutional) and heavy civil engineering projects. Large-scale construction must consider zoning requirements, the environmental impact of the job, the successful scheduling, budgeting, construction-site safety, availability and transportation of building materials, logistics, inconvenience to the public caused by construction delays and bidding, etc.