The STD may tie or permit the tying of Federal-aid highway projects or Federal-aid and State-financed highway projects for bidding purposes where it appears that by so doing more favorable bids may be received. To avoid discrimination against contractors desiring to bid upon a lesser amount of work than that included in the tied combinations, provisions should be made to permit bidding separately on the individual projects whenever they are of such character as to be suitable for bidding independently.

When Federal-aid and State-financed highway projects are tied or permitted to be tied together for bidding purposes, the bid schedule shall set forth the quantities separately for the Federal-aid work and the State-financed work. All proposals submitted for the tied projects must contain separate bid prices for each project individually. Federal participation in the cost of the work shall be on the basis of the lowest overall responsive bid proposal unless the analysis of bids reveals that mathematical unbalancing has caused an unsupported shift of cost liability to the Federal-aid work. If such a finding is made, Federal participation shall be based on the unit prices represented in the proposal by the individual contractor who would be the lowest responsive and responsible bidder if only the Federal-aid project were considered.

Federal-aid highway projects and State-financed highway projects may be combined in one contract if the conditions of the projects are so similar that the unit costs on the Federal-aid projects should not be increased by such combinations of projects. In such cases, like quantities should be combined in the proposal to avoid the possibility of unbalancing of bids in favor of either of the projects in the combination.