Restraint Requirement Analysis

What it does

The clear zone is the lateral strip, measured from the edge of the carriageway, in which an errant vehicle ought to be able to stop or recover without meeting an obstacle or a dangerous side slope. The norm defines two things about it, and the command implements both:

1. How wide it is. A base width tabulated by design speed and average daily traffic, multiplied by a curve factor that widens it through a curve, the more so the tighter the radius and the higher the speed.
2. Whether the terrain inside it calls for containment. For each crest/toe pair found in the section, the norm gives a minimum slope as a function of the embankment height: above that slope the embankment is deemed non-recoverable and containment is indicated.

The command crosses the two along a whole alignment:

• it walks the alignment step by step;
• at each station it reads the design speed, the traffic volume, the carriageway width and the radius from the alignment;
• it computes that side's clear zone and cuts a section of the terrain from the carriageway edge to the outer limit of the clear zone;
• it sweeps that section looking for the most unfavourable crest/toe pair and asks the norm;
• it classifies the station as critical (containment indicated), non-critical embankment or cut/flat.

At the end it prints the count per verdict on the command line, assembles the batch guardrail table rows from the critical stations and opens the section viewer with one section per station.

The command reads and reports; it does not draw. Colouring per station, drawing the sections in the model and exporting to Excel are not available in this version: the numbers go to the command line and the sections to the viewer. Nothing in the drawing is modified.

The tables are not switched by the country profile. This version carries one national standard's clear-zone width table and one national standard's slope thresholds, which do not change with the active profile. The numbers themselves are listed on the Portuguese edition of this page. If your regulator's tables differ, read the verdicts as an indication and check the deciding numbers — which the section viewer shows for every station — against your own norm.

What the alignment has to carry

The command reads three alignment properties, all indexed by station (CSV text, not a loose value):

If VelocidadeDiretriz or VDM are missing (read at km 0), the command warns before running: the clear zone would come out zero and nothing would be flagged, which on screen is indistinguishable from "there is nothing to flag". The radius comes from the alignment's own geometry at the station.

Workflow

1. Run CAPCAD_ANALYTICS_RESTRAINT. The form opens beside the drawing.
2. Set the three numbers the command cannot guess: Step (22), offsetDefensa (36, on the Extra tab) and Wdith polyline seção (8), the half width used when the alignment does not carry its own.
3. Click Analisar taludes das seções ao longo do eixo (7). The form hides while it collects.
4. Select the surface: a selection set of 3DFACE or PolyFaceMesh. If nothing valid is selected, the command warns and stops.
5. Select the alignment: a polyline or a line. If it does not carry speed and traffic volume, the warning described above appears — it is worth cancelling and completing the alignment's properties before going on.
6. The command walks the alignment and prints on the command line: the total of analyses (two per station), the count of critical / embankment ok / cut-flat / no section, how many stations call for a guardrail on each side, and the stretch table.
7. The section viewer opens with one section per station. Step through with < / > (38, 39) or with the slider (40), tick Apenas críticas (41) to see only what matters, and read in the table (42) why that station got its verdict.
8. For a section away from the step's stations, use Analisar talude seção pontual (23) and click a point: it is projected onto the alignment and the section at that station is cut and shown.

The form

The numbers are the same in every figure on this page: 1 to 37 on the analysis form, 38 to 46 on the section viewer. The screenshots are of a Portuguese session; the numbering is the same in both editions.

Most of this form's captions are not translated: an English session shows them in Portuguese, including the first tab's caption, which is a national standard reference. The tables below give each caption as it appears, with an English gloss.

The analysis tab, the form as it opens.

Tab 1: Analysis

Declividade lateral — cross slope (top left frame)

Método Kcz incompatível curvas — what to do when the curve factor is not tabulated

The (speed, radius) pair may simply not exist in the curve-factor table — a tight radius at a high speed is not covered by the norm. This frame says what to do then.

Análise ao longo do eixo — analysis along the alignment (top right frame)

Análise pontual — single-point analysis (bottom frame)

The three footer labels — Tutorial, Civil 3D and LandXML — are not clickable in this version.

Tab 2: Vertical

The Vertical tab has a single button.

Tab 3: Extra

The Extra tab: shortcuts to neighbouring commands and the three numbers that assemble the guardrail stretches.

The section viewer

The viewer at a critical station: red terrain on the right, the pair that decided the verdict in purple with "48,5% / 45,0%" (measured slope against the norm's limit), the clear-zone limits in blue and the two-sided table on the right.

The viewer is read-only: it draws nothing in the model and stores nothing beyond its three display options.

When the viewer is opened by the command, a Ponto… button also appears beside the arrows: it repeats the single-point section (23) reusing the surface and the alignment of the last analysis, without asking again. Hovering over the drawing, the footer shows the offset, the elevation and how far from the edge, and on which side, the cursor is.

The legend colours:

How the options combine

The figures below came out of real runs of the analysis engine over synthetic terrain, at vertical exaggeration 2. A 7 m carriageway (edge at 3.50 m), design speed 100 km/h, traffic volume 3,000 — which gives 8 m of clear zone on each side.

The labels inside the figures are in Portuguese: esquerda is left, direita is right, corte/plano is cut/flat, aterro ok is a non-critical embankment and crítico is critical.

The three verdicts

A 60 % slope starting 2.50 m beyond the edge. The crest sits at the edge itself, so the flat shoulder counts towards the horizontal run: the crest/toe pair accumulates a 3.00 m drop over 7.50 m, that is 40 % average slope — not the 60 % of the slope face. The threshold the table gives for a 3.00 m drop is below that, so the station comes out critical.

The same terrain at 25 %. The drop reaches 1.375 m over an 8.00 m run, that is 17.2 % average slope, far under what the table asks for at that height: there is an embankment, there is no criticality.

Terrain rising to the right: there is no drop at all inside the clear zone, and the side comes out cut/flat. The left-hand side is flat in all three figures, and comes out cut/flat in all three.

How the containment threshold behaves

The table applied is a step function: the higher the embankment, the gentler the slope that already makes it critical. It starts at the shallowest height the table covers and flattens out to a fixed 1V:3H from a certain height upwards; below the shallowest row there is no line at all — that is the waived shallow embankment.

The comparison is strict: a slope exactly equal to the limit does not call for containment.

How the clear-zone width behaves

The base width is read from a table by design speed and traffic volume, and then multiplied by the curve factor. Two properties of that lookup are worth knowing, because they decide whether you get an answer at all:

• the speed must match a table row exactly. A design speed that falls between two rows returns zero and silently zeroes the whole clear zone. Round the alignment's design speed onto one of the table's rows.
• the radius is snapped onto a table row before the lookup. Below the tightest row and from the widest row upwards it is treated as a tangent, and the curve factor is 1. The snapping is downwards except in one band, which snaps up — a deliberate consequence of the table having no row there.

The final width is curve factor × base width.

From critical stations to guardrail stretches

The critical stations arrive isolated, one per step. Each covers from its own station to station + step; contiguous ones become a single stretch. With a gap tolerance and an extra length, nearby stretches join and each stretch gains slack at both ends (here, tolerance 40 m and extra 8 m, only to show the effect — in this version the command uses 0 and 0).

Each stretch becomes one row of the table, with these columns:

Km ini · Km fim · Afastamento · Ação · Bloco entrada · Bloco saída · Terminal entrada · Terminal saída · Bordo ini · Bordo fim · ZL ini · ZL fim · Cor talude

Five columns come out as ?: Ação (action), Bloco entrada/saída (entry/exit block) and Terminal entrada/saída. That is on purpose — the analysis knows where containment is needed, not which guardrail nor which terminal. You fill the five in on the spreadsheet and pass the result to CAPCAD_BATCH_RESTRAINT, which draws it. Cor talude carries vermelho (red) for a stretch that had any critical station and laranja (orange) otherwise.

Remembered between sessions

The form stores the controls of three frames: Wdith polyline seção (8), Analisar cortes até 18m (9), Dispensar para aterros < 0,9 m (10), the five output boxes (11 to 15), the surface (16), the curve-factor method and its value (17 to 19), and the single-point frame — Incluir seção (24), Include grid (25), Exageração vertical (26) and Extrapolação além ZL (27). They are written when the form closes.

Not remembered: the Step (22), Usar largura de via da definição do eixo (20), the 18 m box (21), the Declividade lateral frame (1 to 3) and the whole Extra tab — including offsetDefensa (36).

The viewer stores its three display options — exaggeration, grid and clear-zone limits.

Notes

• The surface is read from entities, not from Civil 3D. Select the faces (3DFACE) or the mesh (PolyFaceMesh) that represent the terrain. The Superfície list (16) sits with the lone LANDXML item and is not used.
• Two surfaces do not add up. When more than one surface is selected, the section used is that of the first one to produce a result, even where another is higher.
• The analysis section stops at the clear-zone limit. What is drawn beyond it (light grey) exists so you can see the slope continue; it never enters the verdict.
• The maximum drop may not be the drop that was judged. The viewer's table carries both rows. The max. drop accumulates any fall seen in the sweep, including those with no horizontal run, while the norm is only consulted when there is a run; so a station can come out embankment ok because of a fall that was never judged.
• One row of the curve-factor table goes beyond the maximum-admissible-speed table. For one radius the curve-factor table carries a value at a speed that the maximum-admissible-speed table does not support for that radius; an alignment at that speed and radius computes normally from the curve-factor table.
• The sign of each row's Afastamento is what states the side: check it against the real slope before sending the table to the batch insertion.
• The command has no keyboard shortcut. ZL is already reserved for CAPCAD_MARKING_AREA_LINEAR.