To ensure that every effort is being made to increase the competition for paving contracts, and that the latest market rate is considered when determining pavement type, contractors should be allowed to bid an alternate pavement design. Future maintenance costs will be considered with a life cycle cost adjustment factor, thus resulting in the most equivalent specifications possible to draw in the maximum number of bidders for MoDOT paving projects. While alternate bidding is generally advantageous for all projects, circumstances occasionally arise which cause one pavement type to be preferred over the other.

For projects less than 2 lane miles, alternate bidding is not required, but the core team should look at pavement options that bring the best value to the project. A lane-mile is defined as pavement 12 ± 2 feet (3.6 ± 0.6 m) wide and 1 mile (1.6 km) in length. Full depth paved shoulder widths that have the same pavement type as the mainline should be proportionally (compared to 12 ft. (3.6 m) width) included when calculating lane lane-miles. Consideration should be given to initial construction cost, long-term maintenance cost, and continuity with existing pavement. Also, impacts to local residents and business along the route should be considered.

Pavements having prevailing issues that make only one type of pavement desirable should be examined to determine the feasibility of alternate bids on pavement. These may include circumstances such as widening existing pavements with safety and durability issues due to differing pavement types in the driving lanes, urban construction, consideration of how the pavement type effects the major item of work for the project (e.g., if major item of work for the project is bridge work the life cycle costs may be insignificant to the total project cost), total amount of paving compared to existing pavement, project staging and project scoping with regard to long-range transportation goals.

In unique circumstances, the core team may determine there is a need to specify one pavement type over another on a project. The core team decision, which will include the concurrence of the Pavement Team member and the Design Liaison Engineer, is documented through the Design Exception process.

Life Cycle Cost Adjustment

For alternate pavements a life cycle cost adjustment factor will be added to the lowest asphalt bid to take into consideration the future rehabilitation cost for each pavement type. This life cycle cost adjustment factor considers future cold milling and overlay of the surface layer of asphalt at 20- and 33-year intervals and diamond grinding of the concrete surface at 25 years. The last published real interest rates from the United States Office of Management and Budget will be used to bring the future costs to present worth. The Design Division will calculate the cost adjustment factor utilizing the most updated information available. Projects that contain an aggregate total of more than 2 lane miles of paving bid as alternate pavements will include the life cycle cost adjustment factor as calculated by the Design Division. Projects with less than 2 lane-miles bid as alternate pavements will have a $0 life cycle cost adjustment factor.

[edit]Plans For Projects with Alternate Pavements
Plans for all projects with alternate pavements should contain:

Typical sections for both alternates, including station limits, and all side road connections.
All pay items for full depth alternate pavements shall be in square yards for the entire pavement surface.
One set of 2B sheets with separate sheets for the items associated with each alternate.
Using the “Estimate 2000” program, the quantities for pavement and other items associated only with the asphalt alternate (designated as “Alternate A”) should be designated as “Section 02” and the quantities for pavement and other items associated only with the concrete alternate (designated as “Alternate B”) should be designated “Section 03”. This will enable summation of the appropriate subtotals to compile an estimated total cost per alternate.
No pay item listed in Section 02 or 03 should be listed in Section 01. This would lead to differing bids and cause confusion when administering the contract. For example, if the base quantities differ, include the appropriate total base quantities in Sections 02 and 03, but not Section 01.
For shoulder rumble strips, include the bituminous rumble strip pay item with the asphalt alternate, and the concrete rumble strip pay item with the concrete alternate.
Design Special Provision ALTERNATE FOR PAVEMENTS DSP-96-04 should be inserted in the Job Special Provisions. The Life Cycle Cost adjustment factor is calculated by the Central Office.
Aggregate total lane-miles of paving. A lane-mile is defined as pavement 12 ± 2 feet (3.6 ± 0.6 m) wide and 1 mile (1.6 km) in length. Full depth paved shoulder widths that have the same pavement type as the mainline should be proportionally (compared to 12 ft. [3.6 m] width) included when calculating lane lane-miles.
Following are design guidelines for different project scenarios:

SEPARATE GRADING AND PAVING PROJECTS WITH 18 IN. ROCK BASE

Subgrade profile and cross sections should be designed for the thicker pavement alternate.
If the thinner option is constructed, the contractor will be responsible for maintaining the profile grade. In the paving project the addition of subgrade material for the thinner pavement design will be paid for as Subgrading and Shouldering, Class 2.
SEPARATE GRADING AND PAVING PROJECTS WITHOUT 18 IN. ROCK BASE

Subgrade, profile and cross sections should be designed for the thinner pavement alternate.
If the thicker option is constructed the contractor will be responsible for maintaining the profile grade. In the paving project the removal of subgrade material for the thicker pavement design will be paid for as Subgrading and Shouldering, Class 1.
Crossroad structures should be designed to accommodate a minimum cover based on the thicker pavement design.
COMBINED GRADING AND PAVING PROJECT

Subgrade profile and cross sections should be designed for the thinner pavement alternate.
The contractor will be responsible for maintaining the profile grade for either alternate pavement with no direct pay.
Crossroad structures should be designed to accommodate a minimum cover based on the thicker pavement design.