Horizontal–Vertical Alignment Phasing Review
Compare horizontal and vertical curve intervals on the same verified station basis.
Identify curve pairs that warrant a plan and profile inspection. Use a shared-scale diagram and an exportable review list.
- •ERA Geometric Design Manual (2013), Chapter 10, phasing review context
- •Alignment designers
- •CAD technicians
- •Design reviewers
Overlap = max(0, earlier end − later start)Start and end stations are in metres. A negative difference before clamping gives the gap.Use these outputs for preliminary checks. They do not constitute official engineering approval. Verify the inputs, method and results against the project criteria before using them for design or construction.
Import curve intervals
Use the template columns for both files. Enter decimal metre stations, to three decimal places, on the same continuous station basis. Each file accepts up to 50 curves.
Confirm both files refer to the same physical alignment, origin and increasing direction. Use matching alignment and basis IDs. Set station_equations to none only after confirming the supplied station values are continuous.
Station basis, method and worked example
Use two interval CSVs from the same physical alignment and continuous station basis. Verify origin, direction and units before assigning the matching IDs in the templates. Resolve station equations outside this tool. The files declare the basis. The tool checks the declarations and cannot verify them against a drawing.
Each interval must have a unique curve ID within its file and a strictly increasing start and end in decimal metres. The tool compares every horizontal span with every vertical span, sorted by start station on each side. Station arithmetic uses integer millimetres. Decimal values beyond three places and stations outside ±1,000,000,000 m are rejected.
Subtract the later start from the earlier end. A positive difference is overlap length. Zero means endpoint contact. A negative difference means a gap. For positive overlaps the review distinguishes partial overlap, containment in either direction and coincident spans. In the example, 1,348.770–1,505.850 m and 1,420.000–1,580.000 m overlap by 85.850 m. The 1,580–1,600 m and 1,600–1,800 m pair touches without overlap.
ERA Geometric Design Manual with appendices 080213.pdf (2013), Chapter 10 §§10.1–10.7, printed pages 10-1–10-2, PDF indices 130–131, and Figure 10-1, printed page 10-4, PDF index 133, describe phasing cases. The arithmetic identifies interval relationships for review. Examine sight lines, hidden dips, nearby disjoint curves and design decisions separately in plan and profile.
Use the horizontal alignment closure tutorial to check source curve stations and the station equation ledger before adapting the template. The practice files are synthetic interval tables for this tool.