Allsite.ai provides basic road layout tools, allowing you to quickly run a Level AI model that has a 'right of way' and single road lanes. It allows definition of longitudinal grades and, if you have a profile associated with the alignment will update the vertical geometry for review (review only, as the roads elevation is set via feature lines for basic road corridors in the Level AI produced proposed surface).
Additionally you can manually draw curbs in, this can be useful for carpark design.
In the future, more basic 'pseudo road corridor' types will be supported including 2 lane boulevards with an island in the middle.
You can use a combination of valid road corridors and layout assist roads in your model, this is sometimes required for carpark / commercial land development design.
Getting Started
To get started you will need polylines or alignments for your road centrelines.
Select them all and convert them to Allsite "Road (Simple Corridor)" objects. This automatically converts the polylines to alignments.
Set the layout related parameters (see below) for things such as distance to back of curb, 'right of way' (ROW) width, cul-de-sac radius, intersection radius.
Set longitudinal grade information (same as for full road corridors)
Run Layout assist
Review modifier locations and configure settings as (same as for full road corridors)
Create road profile views (this also creates a proposed design placeholder profile that will be populated on a subsequent Level AI run).
Tip: You can use QSELECTPROPERTYSET command to select roads of a particular type and configure parameters (ie select all LOCAL road alignments and set their intersection radius)
Road Layout Settings
Setting | Description |
Cul-de-sac radius | Radius of the cul-de-sac bulb at the end of this road, measured to the back of curb — not to the right-of-way. Set to zero for no cul-de-sac. The knuckle / cul-de-sac exit radius is used for the curb returns where the bulb meets the road. |
Cul-de-sac type | Where the bulb sits relative to the end of the centreline. Centre — a symmetric head on the end of the road. Left / Right — the road runs straight through and the bulb is offset to that side. None — no cul-de-sac. |
Knuckle radius | Radius of the knuckle at a sharp bend in this road, measured to the back of curb. A knuckle is added at any corner that turns through less than 150°. Leave blank or zero for no knuckles. See Knuckles at sharp corners below. |
Knuckle / cul-de-sac exit radius | Radius of the curb returns where the straight road curb meets a cul-de-sac head or a knuckle — the curves the road "exits" the bulb on. Measured to the back of curb. One value covers both cases, so a road with a cul-de-sac at one end and a knuckle at a bend uses the same exit radius for each. Leave it blank to use this road's own intersection radius. That is what these curb returns were built at before the setting existed, so existing roads keep the geometry they have and you only need to fill it in where you want the exits to differ from the intersections. Zero is read the same way, not as a square corner. Ignored on a road that has neither a knuckle nor a cul-de-sac — that is, where the cul-de-sac radius and the knuckle radius are both zero or blank. |
Intersection radius | The intersection radius. The 'lesser' road type will take precedence for radius (for example a LOCAL road intersecting with an ARTERIAL road will use the LOCAL road's radius) Also used for the knuckle and cul-de-sac curb returns on any road whose exit radius is left blank. |
Distance to back of curb (left and right of centre) | Distance from the road centreline to the back of curb, left / right of centre. Note: leave the right blank and both sides use the left value. |
Width centre to ROW (left and right) | Width of the right-of-way from the centreline, left and right. Must be greater than the distance to back of curb. |
New Road (Simple Corridor) objects take their layout dimensions from the Road layout parameters table in your project's Layout Assist settings, under Simple Corridor Generation. The row is matched on the road's Road Category, and the LOCAL row is the fallback for any category that has no row of its own. You can override any of these values on an individual road afterwards.
Knuckles at sharp corners
You do not draw the knuckle. Draw the road centreline through the corner as you normally would, set Knuckle radius on the road, and layout assist widens the corner when it runs.
A knuckle is added where all of the following are true:
The centreline turns through less than 150° — either at a vertex inside one centreline, or where two centrelines meet end to end.
The road has a knuckle radius greater than zero. Where two roads share the corner, the larger of their two radii is used.
The knuckle fits inside the earthworks extent.
The corner is clear of a cul-de-sac — a bend just before a turning head keeps the head alone.
Where three or more roads meet, the corner is an intersection rather than a bend and takes the intersection radius instead. The curb returns out of a knuckle use the knuckle / cul-de-sac exit radius.
With no knuckle radius set, a sharp corner is still rounded to the road's own half width, so the curb turns convex around the outside of the bend rather than pinching into it.
Defining Sub Assembly for Modifiers
You can add a curb subassembly to the generated modifiers. This will result in Level AI producing all design feature lines in the final model
To do this, follow these steps:
Add an assembly to your model that has the sub assemblies you want.
To populate the property data set with these new curb sub assemblies you will need to run a "Fix Schema" command (or close and re-open the DWG).
Use the property data set select to select all generated modifiers that are not the 'extent / outside edge'.
Update the Sub Assembly on the modifier
If using manually drawn modifiers that are within a carpark / not using layout assist you can set the direction of the modifier, the symbology updates to indicate the gutter side.
Set the Insertion Point to say which point of the curb cross section the line you drew represents. The options are the Civil 3D subassembly point codes:
BACK CURB (default) - back of curb, point code Back_Curb
TOP CURB - face of curb at the top, point code Top_Curb
FLOWLINE GUTTER - gutter invert / lip, point code Flowline_Gutter
FLANGE - outer edge of the gutter where it meets the carriageway, point code Flange
The rest of the cross section is placed relative to that point, so the same sub assembly can be used whichever line you have drawn.
Insertion Point only applies to manually drawn / layout assist modifiers. Modifiers extracted from a road corridor are always the back of curb line.
The sub assembly also needs the matching point code on its surface shape - if it does not have one, the insertion point is ignored and the cross section is used with a back of curb insertion point.
Note - if you run Level AI prepare prior to adding subassembly types, validation warnings "NoSubassemblyType" will be added, this is resolved by following steps above.
Demo
Click below for a step by step walk through to create a pseudo road corridor.
