The most revealing sentence in Ohio’s plans manual is about files rather than drawings. Contractors on a state project receive the design model, and the manual sets out what that model is worth against the paper.
Unlike electronic image files (i.e., PDF images) that are part of the contract documents, CADD files (i.e., basemap files) provided to contractors are for reference purposes only.
In a conflict between the two, the bidding documents take precedence. The sheets are therefore neither a description of the finished road nor the richest description of it. They carry what could not be written as prose or standardized across projects, and their conventions exist to keep every one of those items traceable to the decision behind it.
The sheet order encodes the dependencies
Ohio requires plan components to appear in a fixed sequence whenever they are required at all. Title sheet, then schematic plan, typical sections, general notes, maintenance of traffic, general summary, subsummaries, calculations, project site plan, plan and profile for the mainline and then for side roads and ramps, cross sections in the same two groupings, superelevation tables, details, drainage, traffic control, lighting, landscaping, and structures last.
Washington splits the set across volumes, and the split is informative. Its first volume holds only the complete index, the vicinity map and the summary of quantities. The second opens with certification sheets and the borrow, pit, quarry and waste site plans, then roadway sections, grading sections, stage construction plans, alignment, and quantity tabulation sheets placed immediately before the plan sheets showing the work being tabulated.
Absences carry meaning too. Washington’s sequence notes that roadway profiles are normally only required when the grade is being revised, and that where only part of the vertical alignment changed, only that part needs one. A set without a profile series is usually recording that the grade was left alone.
The title sheet is an index and a disclosure at once
The index of sheets serves as the table of contents for the entire set. Ohio numbers sheets sequentially, requires any unused number to be noted as “Not Used”, and permits late insertions to be alphabetized as P.88A, P.88B and so on, with the rule that the last actual sheet number is never alphabetized. Final numbering is usually deferred until the Stage 3 review, because sheets get added, deleted and rearranged throughout design.
Two tables on that same sheet do more work than their size suggests. One lists the standard construction drawings applicable to the project with their current revision dates, grouped by set. Those drawings are published in three sets, roadway, bridge and traffic, and the roadway series codes are a small vocabulary of their own: BP for base pavement, CB for catch basins, MGS for guardrail, HW for headwalls, I for inlets, MH for manholes. The second table lists design exceptions by feature, approval date and sheet number, and where a project has none the manual requires the words “None Required” rather than a blank. That table is the visible end of the federal exception machinery described in the standards that shape roads, which allows approval on a project basis for designs that do not conform to the minimum criteria.
Signatures follow different conventions in different states. Ohio requires plans to be digitally signed and sealed by a registered professional engineer or surveyor, with the signature block and seal on the title sheet, where a single seal is assumed to cover the entire plan unless the drawings say otherwise. Washington instead places the licensee’s seal on all plan sheets, exempting a named list on design-bid-build work.
Station and offset is a coordinate system with a history built in
Highway plans locate everything by distance along a reference line rather than by coordinates. Ohio states the notation directly: 104+59.35 means 10,459.35 feet from station 0+00. Tick marks appear at full stations, meaning 100-foot intervals, and where an intermediate point drops its full station designation the leading zeros are kept, so +03.17 abbreviates station 2+03.17. Stationing increases in the direction of the straight-line mileage for the county, route and section, and the schematic plan is generally oriented so that mainline stationing increases from left to right regardless of where north lies.
The feature that surprises newcomers is the station equation, indicated on the reference line by stating the station back and the station ahead. Alignments get revised after stationing has been established, and rather than renumber every downstream reference the designer records the discontinuity. A route can therefore be longer or shorter than the difference between its first and last station.
Offsets are perpendicular distances from that reference line, with a side designator, and one ambiguity in them is documented rather than hidden. Where a centerline carries a deflection angle without a horizontal curve, Ohio acknowledges the confusion about measuring from the back or the forward tangent in the resulting overlap area, resolves it with a figure, and identifies a further blind area where neither tangent works. Stations and offsets there are measured off an extended back tangent and annotated to say so.
Precision is its own signal. Washington uses the precision of the best information available, so a right-of-way offset at station L 14+00.00 with an offset of 60.00 feet may be shown as L 14+00 at 60 feet, while an offset of 59.99 feet is shown as 59.99 and not rounded. Paving, pavement marking, signing and traffic control plans are named as the sheet types where the nearest foot or tenth of a foot may suffice instead.
A typical section is a rule, not a place
The typical section is defined as a portrayal, with dimensions, of how a cross-sectional view of the roadway would appear after construction is completed, and its conventions follow from that definition. Sections are shown relative to the direction of increasing stationing regardless of the direction of travel, the vertical scale of the pavement thickness may be exaggerated so the layers stay legible, existing ground and pavement are drawn dashed, and no scale is shown on the sheet at all.
A separate section is required wherever something changes: the pavement build-up, the type of median, the beginning or end of guardrail and concrete barriers, an added or dropped lane, and superelevated areas. Under each, the station limits where it applies are stated. A set with fourteen typical sections describes fourteen regimes along the alignment, and those station limits are the map from rule to ground.
Plan and profile sheets carry three things at once
A plan and profile sheet is composed of three distinct parts, plan, profile and quantities, which may share a sheet or be separated when the work is too dense. Rural projects are drawn at one inch to fifty or twenty feet horizontally against one inch to five or ten feet vertically, urban work at one inch to twenty feet. Ohio notes the coverage those scales produce, about 1,500 feet of alignment on a sheet at the fifty-foot scale and 600 feet at the twenty-foot scale.
Every profile on a highway plan is vertically exaggerated, because those pairings put the vertical scale between two and ten times the horizontal, so a grade that looks alarming on the sheet is a fraction of what it appears to be. The number that settles it is written on the sheet as a percentage to the hundredth.
At the ends of a project the sheets run past the work, by a minimum of 300 feet of additional existing topography beyond the ends of permanent pavement construction for design speeds of 40 mph or less and 500 feet above that. Where work or quantities continue onto another sheet, a match line is drawn and its station given, recommended at a multiple of 100 feet.
The link between a drawing and a payment is the reference balloon. Balloons tie items on the plan to the pay quantities in the estimated quantities table, dashed balloons indicate that the quantity is picked up on a different sheet, and drainage balloons are numbered uniquely for each structure and conduit run and never reused within the same plan set. Their letter prefixes are a shorthand for the trade: UD for underdrain, GR for guardrail, D for drainage structures, P for conduit, C for curb, R for removal. Those structures are treated in how highway drainage systems work.
Cross sections are the earthwork ledger
Cross sections exist mainly to show end areas and surface dimensions for the calculation of earthwork and seeding quantities, which is why their geometry is unforgiving. They are plotted on a one-inch grid with horizontal and vertical scales equal, usually one inch to five or ten feet, so unlike the profile they are undistorted, and where an exaggerated section does appear it is for a stated purpose such as variable depth leveling course quantities.
Stationing on these sheets increases from the bottom to the top. The station is shown in bold print under each section at the centerline of construction, with the existing ground elevation at that centerline directly below it and the proposed grade at the profile grade point directly above. Regular intervals are normally 50 feet, tightening to 25 where greater detail is required, with additional sections at abrupt ground line changes and at drives, bridges and drainage items. The volumes these sheets generate are the subject of earthwork and grading.
Quantities have to be traceable back to a sheet
The rule Ohio states for estimated quantities holds the whole set together. Quantities are to be calculated and presented so that they may be traced from the general summary sheet to their origin through a system of cross-referencing. Sheet number columns point back at the sheets the quantities were carried from, and subsummaries exist because those columns run out.
The general summary is also where a project’s financing becomes visible on paper. Pay quantities are separated according to participation by the involved agencies, with a separate subtotal for each unique combination of local, state and federal fund participation and for all incidental pay items, in addition to the grand total. The summary has to be an Excel file built on the standard CTY-PID-GENSUM spreadsheet, because its contents transfer directly into the estimating office’s AASHTOWare software to create the proposal for advertising and bidding.
Those subtotal columns are the plainest thing in the set, and checking a project’s record against more on research resources mostly means reading them alongside the design exception list on the title sheet. Long after the road opens, the two tables are still the record of which agency agreed to pay for which line item and which criteria the project was excused from meeting.