136.8 Preliminary Design

Dimensional Accuracy

Table 136.8.2 Dimensional Accuracy

136.8.1 Design Criteria

As described in 136.1 General, the engineer of record will be considered responsible for determining the appropriate design parameters for the project using good engineering judgment based on the specific site conditions, local agency needs and guidance provided in this article. The design criteria selected by the engineer of record shall be noted on the plans. The local agency and the engineer of record shall be responsible for keeping the design justification on file for all federal aid projects, and the records shall be available for review by MoDOT and FHWA if requested. The current edition of the following publications or any local ordinances should be followed as a guide with modifications as considered appropriate by the engineer of record and to be in keeping with good engineering practice:

Engineering Policy Guide, by MoDOT

A Policy on Geometric Design of Highways and Streets, by AASHTO

Guidelines for Geometric Design of Very Low-Volume Local Roads (ADT < 400), by AASHTO

Roadside Design Guide, by AASHTO

Highway Capacity Manual Manual for Railroad Engineering, by AREMA

Traffic control devices shall be governed by the Manual on Uniform Traffic Control Devices (MUTCD).

The National Cooperative Highway Research Program (NCHRP) has issued guidance, Report 350, on the standards for guardrail and bridge railing design. This new guidance is required by FHWA to be incorporated into projects that are located on the National Highway System (NHS), and may be considered for use by the local agency for projects located off of the NHS. (Refer to 136.8.7.7 Bridge Rail System for additional information).

The Americans with Disabilities Act (ADA) requires that all facilities be designed to current accessibility standards to the maximum extent feasible for sidewalks, crosswalks, grades, etc. The Americans with Disabilities Act Accessibility Guidelines (ADAAG) have been adopted as standards by the Department of Justice and the Department of Transportation for accessibility standards for buildings and sites. Standards for pedestrians in the public right of way are yet to be approved, but the Public Right of Way Access Guidelines (PROWAG) may be used. Refer to ADA Resources for more information.

136.8.2 Accuracy

Table 136.8.2 lists detail design information for the accuracy of plan dimensions. This chart is a guide to assist users in the transition to metric plans production, and can be varied as needed.

Table 136.8.2 Dimensional Accuracy

Dimension		English Accuracy	Metric Accuracy
All stationing		0.01 ft.	0.001 m
Topography
	Stationing	1.0 ft.	0.1 m
	Offset	1.0 ft.	0.1 m
	Angle	0 degrees 01 minutes	0 degrees 01 minutes
Bearings and Angles		0 degrees 00 minutes 1 sec	0 degrees 00 minutes 1 sec
Right of way
	Stationing	0.1 ft (1.0 ft. or 5.0 ft. preferable)	0.01 m (0.1 m or 1 m preferable)
	Width	1.0 ft. (5.0 ft. preferable)	0.1 m (1 m preferable)
Area		0.01 acre or 1.0 ft2	0.001 hectare or 0.1 m2
Referenced Points
	Stationing	0.01 ft.	0.001 m
	Ties	0.1 ft	0.05 m
Bench Marks
	Stationing	1.0 ft.	0.01 m
	Offset	1.0 ft.	0.01 m
	Elevation	0.01 ft.	0.005 m
Profile Grade
	P.I. station	0.01 ft.	0.001 m
	P.I. elevation	0.01 ft.	0.005 m
	Rate of grade	0.001% (where practical)	0.001% (where practical)
Length of vertical curve		10 ft. increments	5.0 m increments
Stopping sight distance		5.0 ft.	1.0 m
"K" factors		Nearest whole number	Nearest whole number
Flow line elevation		0.1 ft.	0.01 m
Items to be constructed
	Stationing	0.1 ft. (1.0 ft. preferable)	0.01 m (0.1 m preferable)
Culvert lengths		1.0 ft. (or next even foot for metal pipe culverts)	0.1 m (or next multiple of 300 mm for metal pipe culverts)

136.8.3 Preliminary Submittals

For all projects, submittal of preliminary plans to MoDOT district offices is required. MoDOT’s review will be limited to ensuring the project meets the intent of the federal-aid program. Specific questions should be provided by the engineer or local agency in writing on their cover letter with the preliminary submittals.

For projects involving bridges or culverts, submittal of preliminary bridge plans, hydraulic studies, etc. to Bridge Division are not necessary. However, if the engineer or local agency has specific questions regarding project eligibility that they would like MoDOT to address at the preliminary stage then Bridge Division is receptive to this information. Specific questions should be provided by the engineer or local agency in writing on their cover letter with the submitted package to the MoDOT district office.

The Categorical Exclusion, Environmental Assessment, or Environmental Impact Statement must be approved by FHWA prior to 35% plan completion. (Note that the Section 106 (historic properties) clearance must also be approved before right of way acquisition can begin).

136.8.4 Traffic Signal Warrants

When the project is on MHTC right of way the local agency should submit signal warrants prior to the preparation of traffic signal plans. Signal warrant forms are available at the MoDOT district office. Traffic counts which are recorded for time intervals of less than one hour should be subtotaled for each hour in order to facilitate proper review of warrants.

The engineer of record shall determine signal warrants based on the MUTCD for all other projects.

136.8.5 Railroad Crossings

If the proposed improvements are on or cross railroad right of way, the railway company must be contacted. Railway company approval will be necessary to receive construction authorization. The local agency must contact the affected railway company directly.

136.8.6 Utility Relocations

The local agency has the ultimate responsibility of negotiating with local utility companies, crossstate pipelines and other utility facilities for right of way, easement and adjustment agreements for utility relocations. The local agency is encouraged to work with each utility to minimize impacts to the utility facilities. An example of a Utility Scoping Checklist is available to be utilized.

The local agency should, in the preliminary phase, identify existing utility locations and determine if any adjustments will be required. Local agencies should consult Program Guide – Utility Adjustments and Accommodations on Federal-Aid Highway Projects, published by FHWA, for assistance regarding utilities within the highway corridor.

All utility adjustments located on MHTC right of way shall conform to the Code of State Regulations, Title 7, Division 10, Chapter 3 – Utility and Private Line Location and Relocation. The cost of necessary utility relocations for which the local agency is responsible is eligible for federal participation. If the local agency elects to receive federal participation, utility agreements must conform to 23 CFR Section 645A, which is the applicable Federal Regulation regarding utility relocation on federally funded highways. MoDOT can assist the local agency with information about the above regulation.

Actual Cost Agreements are utilized when certain costs are unknown and the actual amount for the adjustment will be reimbursed. Lump Sum Agreements are used when costs are static and can be determined ahead of time. Provisions for the audit should be stated in the agreement between the utility and local agency. Sample Utility Agreements on Lump Sum and Actual Cost are available.

Utility relocations that impact MHTC right of way require prior MoDOT approval for the plan(s) of adjustment(s). Each plan of adjustment must be submitted to the district liaison engineer for review and approval prior to final PS&E approval. The utility company will be required to acquire the necessary MoDOT permits prior to any work being performed.

MoDOT is not a member of Missouri One-Call (800-DIG-RITE). Some work on projects that affect MoDOT right of way may be in the vicinity of MHTC/MoDOT utility facilities, which included but is not limited to traffic signal cable, highway lighting circuits, ITS cable, cathodic protection electric cable, etc.

136.8.7 Alternate Paving

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, local agencies may allow contactors to bid an alternate pavement design. For further information contact your MoDOT district representative or consult Alternate Pavement.

136.8.8 Bridge Replacement and Rehabilitation Projects

136.8.8.1 Design Parameters

As described in 136.1.2 Federally Funded Bridge Projects, the engineer of record will be considered responsible for determining the appropriate design parameters chosen for the project using good engineering judgment based on the specific site conditions, local agency needs and guidance provided in this article.

The current edition of the following publications should be followed as a guide with modifications as considered appropriate by the engineer of record and to be in keeping with good engineering practice:

A Policy on Geometric Design of Highways and Streets, by AASHTO.

Guidelines for Geometric Design of Very Low-Volume Local Roads (ADT ≤ 400), by AASHTO.

Highway Drainage Guidelines, by AASHTO.

Standard Specifications for Highway Bridges, by AASHTO.

Manual for Railroad Engineering, by AREMA.

136.8.8.2 Funding

Rehabilitation will be considered for the HBP funding when that option of improvement provides the best value while meeting the needs of the local agency. If determined at the Program Eligibility Review project stage that structure improvements are eligible only for partial federal participation in funding as needed to rehabilitate the structure, the local agency may still elect to replace the structure, rather than to rehabilitate the existing structure. However, the amount of eligible federal funding will be limited to that which will not exceed the rehabilitation cost estimate unless appropriate justification is provided by the local agency that a new structure represents the best value. If the rehabilitation cost is at least 68% of the replacement costs, it can generally be assumed that the new replacement structure will provide a better value than the rehabilitation of the existing structure and therefore a better use of federal bridge funds.

136.8.8.3 Deficiencies

The following provides the engineer more detail concerning the 2nd criteria in 136.1.2 Federally Funded Bridge Projects. For existing bridges, the bridge deficiencies are indicated by the bridge inspection report. The inventory criteria will be based on 753 Bridge Inspection Rating as well as the latest version of the FHWA publication Recording and Coding Guide for the Structural Inventory and Appraisal of the Nation's Bridges. An inventory item is considered deficient when the condition/appraisal rating meets the definition as given below.

Definition of Deficiencies

1	Item 58	Deck Condition	< 4
2	Item 59	Superstructure Condition	< 4
3	Item 60	Substructure Condition	< 4
4	Item 62	Culvert Condition	< 4
5	Item 67	Structural Evaluation rating	< 3
6	Item 68	Deck Geometry	< 3
7	Item 69	Under Clearance	< 3
8	Item 71	Waterway Adequacy rating	< 3 and last digit for
	Item 42	Type of Service	= 0, 5-9
9	Item 72	Approach Roadway Alignment	< 3

The bridge improvements should remove any deficiency as listed above and shall be designed to provide an increased life expectancy of at least 25 years before significant deficiencies develop unless the proposed deficient item may remain based on MoDOT’s approval. For a proposed deficient item, the engineer of record is required to provide documentation as to why the proposed parameter should be used and MoDOT will forward as appropriate to FHWA for their approval.

136.8.8.4 Structure Type

The structure type shall be determined by the engineer of record for all span type bridges or culvert type bridges and shall be based on economic comparisons, site specific conditions and local agency needs.

Although not all inclusive, the following gives the engineer of record additional guidance regarding some of the design parameters that generally have a major influence on the eligibility of a bridge project.

136.8.8.5 Truck Loading

For rehabilitations and replacements, variations from AASHTO HS20 design loadings are permissible provided, the minimum load capacity of the superstructure is designed or strengthened so that Item 67, Structural Evaluation from the FHWA coding guide, will not be considered deficient.

136.8.8.6 Bridge Width

The bridge width, as a minimum, shall be improved or built to at least a width where the bridge would not be considered functionally obsolete due to deck geometry based on the number of traffic lanes and future design year AADT or type of roadway classification. This minimum width shall be verified by the engineer of record prior to submittal in accordance with the FHWA coding guide.

136.8.8.7 Bridge Rail System

The appropriate bridge rail and approach railing may be determined by the engineer of record based on site specific conditions such as accident history, AADT, speed, sight distances, roadway width, etc.

For AADT≤400, the use of standard height and/or crash-tested railing is optional. For discussion of the subject, AASHTO’s Guidelines for Geometric Design of Very Low-Volume Local Roads may be consulted. The local agency and engineer of record may select from a variety of curbing or railing types deemed to be suitable for use based on site specific conditions such as accident history, geometric alignment, height of bridge, etc.

136.8.8.8 Seismic Requirements

The level of seismic protection for a particular project is optional and should be determined by the engineer of record and local agency based on agency needs and site-specific conditions such as emergency route status, AADT, functional classification, structure importance, etc.

136.8.8.9 Hydraulics for New Structures

The engineer of record with the local agency’s assistance is considered responsible for the investigation of field conditions related to the hydraulic design of the structure, investigation for FEMA design restrictions as related to the National Flood Insurance Program, and investigation for scour potential, embankment protection and potential channel modification requirements. Impacts on upstream properties should always be considered along with other investigations that may also be found to be appropriate. It is advisable for the waterway opening of the new structure to be designed so as to not result in more adverse flooding conditions from those that would occur with the existing structure, assuming the existing structure is already performing adequately.

As a minimum, the bridge should also be sized appropriately so that the hydraulic performance will not result in a deficient NBI Item 71, Waterway Adequacy rating, and the new structure will not be susceptible to future significant damage caused by flooding based on the engineer’s scour and drift assessment. It is generally not necessary for the engineer of record to submit the hydraulic calculations and report to MoDOT. However, the local agency should keep this information for their own records and make available to MoDOT and/or FHWA if requested.

136.8.8.10 Federal Emergency Management Agency (FEMA) and Required Certifications

Local agencies that participate in the NFIP have the responsibility to ensure that floodplain developments meet the regulations established by the NFIP as identified in the Title 44, Code of Federal Regulations, Parts 59 through 78. Further information on Floodplain Development and FEMA Certifications can be found in 136.4 Environmental and Cultural Requirements.

136.8.8.11 Channel Modification

Channel changes alter the conditions of the natural waterway and may cause an increase in velocity of the flowing water, sometimes resulting in damage to the highway embankment near the stream or excessive scour around footings of structures. Channel modification should be minimized to the fullest extent practical. Where such change is unavoidable, an evaluation must consider the environment, hydraulic, legal, and geomorphic aspects involved. Detailed information on channel modification can be found in 136.4 Environmental and Cultural Requirements.

136.8.8.12 Geotechnical Investigation

The geotechnical investigation of the project should be as determined by engineer of record in order to adequately perform the foundation design and determine side slope and spill slope requirements at bridge abutments.

136.8.8.13 National Highway System (NHS)

In the event of a non-state bridge project being located on the NHS, the design standards given in the federal-aid policy guide Title 23, Subchapter G, Part 625-Design Standard for Highways shall be followed with the following exception. A design vehicle truck loading factor of 1.25 applied to the AASHTO HS20 loading (1.25 times the AASHTO HS20 loading) is required (HS25) unless suitable justification is provided by the local agency and engineer of record for a reduced loading.

136.8.8.14 State-Owned Right of Way

When a state-owned roadway is to be crossed by a bridge, the applicable MoDOT requirements should be followed with vertical and horizontal clearances subject to approval by a MoDOT district engineer. It is recommended that the proposed vertical and horizontal clearances be submitted for MoDOT review and acceptance as soon as possible in the early stages of the project.

136.8.8.15 Sidewalks

Sidewalks are an eligible feature on bridge structures where such access currently exists for pedestrian or combined pedestrian and bikeway use.

136.8.9 Retaining Walls

For installations which are permitted to be located on state-owned right of way, guidance from the current edition of the Standard Specification for Highway Bridges by AASHTO along with applicable MoDOT requirements should be followed. For local agency owned routes, the above may be used as guides or local building codes and ordinances may be used as considered appropriate by the engineer of record to be in keeping with good engineering practice.

136.8.10 Pedestrian Bridges

136.8.10.1 Design Parameters

The engineer of record shall determine all design parameters based on consideration of published AASHTO guidelines and/or local building codes and ordinances except as discussed below.

136.8.10.2 State-Owned Right of Way

When a state-owned roadway is to be crossed by a pedestrian structure, guidance from the applicable AASHTO documents and MoDOT requirements should be followed with vertical and horizontal clearances subject to approval by a MoDOT district engineer. It is recommended that the proposed vertical and horizontal clearances be submitted for MoDOT review and acceptance as soon as possible in the early stages of the project.