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Road Settings

Add longitudinal information to your road corridors

Written by Allsite Support

Pre-requisite - road corridors and intersections have been created in your DWG in one of the supported road corridor format's:

- Civil 3D Road Corridors

- Generate Road Corridor (Allsite builds the corridor, intersections and cul-de-sacs from your road centrelines)

Road Settings (Allsite.ai)

Default road grade data is inherited on project creation. These will be used as default parameters when the road type is changed within your Civil 3D model. By default every road inherits the LOCAL road type longitudinal settings, which can be changed on each road's Road (Simple Corridor).

A road whose values differ from the project's Road Settings is listed in the Settings Report after a Prepare; see Project settings, feature values and the Settings Report.

Default road/rail grades

The Default road/rail grades table, under Roading Standards in the project's road settings, has one row per road type. Its values are the defaults a road takes when it is created or its road type is changed.

Column

Description

Type

The road type the row applies to. There is one fixed row for each road type.

Min grade (%) / Max grade (%)

The longitudinal grade range Level AI keeps the road within. Copied onto each road, where it can be changed per road.

Min sag K, Min crest K, Max K

The vertical curve limits Level AI designs the road within. Copied onto each road, where they can be changed per road.

Min grade change to require vertical curve (%)

A change in grade smaller than this needs no vertical curve. Read for the road's type at each Level AI run.

Crossfall (%)

A simple road's default crossfall comes from Crossfall Centre to Curb (%) in the Road layout parameters table (Layout Assist settings), and Generate Road Corridor builds the road's lanes at it. See Road Layout Settings. A corridor road takes its crossfall from its assembly.

Assess horizontal curves

Coming soon.

Min grade curb transition (%)

Coming soon.

Design vehicle, Design vehicle height, Design speed

Not currently used.

Editing road settings (i.e. longitudinal grade) per road

After Corridors, intersections, knuckles and cul-de-sac's have been created you can go in and customize longitudinal grade information and other road settings on each road's Road (Simple Corridor): select the road's centerline alignment and edit its Extended Data. Roads built by Generate Road Corridor already have one. For a corridor you built by hand, first select each road's centerline alignment and choose Allsite Draw/Convert > Roads > Road (Simple Corridor).

Select the road's centerline alignment and edit its road settings on the Extended Data tab.

Road tangents can be overridden at road-earthworks extent boundary by editing the Tangent Overrides on the road's Road (Simple Corridor) extended data. They are no longer on the plain Allsite road alignment.

If you want your road to interface with a future stage (and existing ground does not match the levels the future stage will be at) you can 'pull back the earthworks extent' - this gives Level AI room to interface the levels with existing ground.

Remember to add a overland flow path between the road and the earthworks extent if you pull back the earthworks extent - this tells Level AI that the road can drain out via earthworks extent (i.e. be a low point)

Road Settings (Applied to the Simple Road)

A road's design settings are set on its Road (Simple Corridor), the Allsite road object on its centerline alignment, and nowhere else. As well as the settings below, it carries the inlet/catchpit spacing and flow limits, Allow Seesaw, Pregrade Offset, and the Lot Layout (Left) and (Right) settings used by Generate Parcels. A road that has corridor regions but no simple road is designed with the project's defaults, and Level AI Prepare warns RdRegionNoSimpleCentreline; see Troubleshooting validation errors.

You do not need to configure settings on curb return assemblies. A curb return has no grade settings of its own: it takes its levels from the edges of the two roads it joins, so its grade follows from those roads' grades and crossfalls. There is no separate maximum curb return grade.

Setting

Description

Road Category

This maps to the settings configured for you Allsite.ai project on the web. Changing the type will revert most longitudinal grade parameters to the projects default.

Network Placement

Informs Service AI where the storm, sanitary and water supply mains run within the road corridor, and where the hydrant line runs. These inherit the network placement and hydrant placement settings configured in your Allsite.ai project on the web, and can be changed per road. An offset from the corridor extent always runs into the road reserve, whatever its sign, for the mains and the hydrant line alike.

Hydrant Offset Feature, Hydrant Offset and Hydrant Side set where hydrants may sit along the road: the feature the offset is measured from (curb, centerline or corridor extent), the offset distance, and the side of the road. Set Hydrant Offset Feature to None for no hydrants along that road. Changing the offset feature re-derives the offset from the project's hydrant placement parameters. See Storm / Sanitary Networks for the project settings.

Min/Max Grade

Defines the bounds that Level AI will vary the design to meet requirements. It is recommended to not over constrain the grade to give Level AI ability to grade.

Max K and Min Sag K, Crest K

Defines longitudinal bounds for the road to be designed with.

What the assembly still provides. The Road Region property set on a Civil 3D assembly is shared by every road that uses that assembly, so it does not hold road settings, and values set on an assembly in an older drawing are ignored. It keeps only what is measured from the corridor: section ID, distance to back of curb, width centre to ROW, cul-de-sac radius and type, and the crossfall read from the assembly's lane subassemblies.

Modifier Settings (Applied to Sub Assembly)

Setting

Description

Pit spacing

Informs Service AI of the spacing of catch basin / catch pits along the road.

Network offsets

Informs Service AI where services can be placed relative to the curb.

Crossfall After

If no subassembly is provided defining the grade of road corridor after the current subassembly it uses this field. If none is defined it will default to 2%.

Tangent Overrides (Applied to the Simple Road)

Setting

Description

Start/End Level Override

Override for the road tangent at connection to earthworks extent.

If defined, a Start/End tangent grade is required as well.

If not defined uses existing ground elevation at road-earthworks extent boundary.

Start/End Tangent Grade Override

Override for the road tangent grade at connection to earthworks extent.

If not defined uses the grade of existing ground at road connection (samples 2 points at road-earthworks extent boundary 2 foot apart)

Sawtooth Control

When Saw-tooth roads on is enabled, Level AI can create saw-tooth (seesaw) road profiles — alternating high and low points along a road — so a flat road drains to its own low points instead of running deep into cut. These project settings are under Road Profile Settings, apart from Set road low points at inlets, which is under Network Settings. The numbers in the diagram match the numbered rows in the table.

Three drawings of a road profile, all long sections along a road centreline, draining left to right. Top, what the Saw-tooth roads on switch does: with it off, the road must fall to an outlet at its own minimum grade the whole way, so on flat ground it runs steadily away from the existing ground and ends up deep in cut; with it on, the road is shaped into teeth that each drain to their own low point, so it only has to fall gently overall and stays near the ground. Middle, one saw-toothing road with three dimensions on it: the maximum highpoint to highpoint length, from crest to crest; the minimum highpoint fall, from each crest down to the next crest downstream; and the maximum ponding depth, from each sag up to the crest downstream of it. A faint crest line runs through the crests showing them stepping down toward the outlet. Bottom, the vertical curve where a road section meets what it ties into, which is every intersection approach and every tie-in to the existing road or ground: the longer curve the road grade table's minimum crest K would ask for is drawn faintly behind the shorter curve the start and end K-value cap allows. The cap can only shorten these curves, never lengthen them. The drawing carries no figures; the key gives each setting's shipped default, imperial first and then metric: saw-tooth roads off, 500 feet or 150 m between highpoints, a 1 foot or 0.3 m highpoint fall, a 1 foot or 0.3 m ponding depth, and a K-value cap of 13 feet or 4 m per 1 percent.

Setting

Description

1 Saw-tooth roads on

Master switch. On, Level AI may shape a flat road into teeth that each drain to their own low point, so the road stays near the ground instead of falling the whole way to an outlet. Off by default. Settings 2–4 only apply when this is on.

2 Maximum highpoint to highpoint length

The furthest one crest (high point) may sit from the next. It is a cap: teeth are shortened further where the road's own minimum grade needs it. Default 500 ft / 150 m.

3 Minimum highpoint fall depth

The least each crest must sit above the next crest downstream. Together with setting 2 it sets how steeply the crests step down toward the outlet. Default 1 ft / 0.3 m.

4 Maximum ponding depth

The deepest a sag (low point) may sit below the crest downstream of it. Default 1 ft / 0.3 m.

5 Minimum road start and end K-value cap

Relaxes the road grade table's Min K at both ends of every road section — every intersection approach and every tie-in to the existing road or ground — so the vertical curve fits. It can only shorten those curves; set above the grade table's Min K it changes nothing. 0 = no curve. Applies whether or not saw-tooth roads are on. Default 13 ft / 4 m per 1%.

Set road low points at inlets

Sets road profile low points at inlet locations so surface runoff drains toward them. Applies when saw-tooth roads are on. Off by default. Shown as Set road low points at catchpits on NZ, AU, UK and Irish projects. Not in the diagram.

One road can opt out on its own: turn off Allow Seesaw on its Road (Simple Corridor) in Civil 3D. It is on for every road by default.

For manual, location-specific control over where high and low points occur, draw a Road Profile Control line — this forces a sawtooth high or low point at a chosen crossing on the road centreline.

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