Alternative approach to Corridor/Template Design - 3D Linear Method

Fellow Engineers, Modelers, Bentley Operators, etc.

Last year in July 2017 at the 9th International Visualization In Transportation Symposium I presented an abstract detailed an alternative approach to working with Corridor/template design.

This approach is called "3D Linear Method". It is the complete opposite on what Bentley encourages in their teaching workshops, and consequently the opposite what is demonstrated by every major Department of Transport I have encountered. A brief outline on how it works:

Instead of single templates/corridors spanning the whole width of each roadway alignment, the corridors are broken up by element. 1 corridor per curb, lane, shoulder, guard rail, end condition, wall, barrier, etc. Each piece is connected to each other, eventually connecting directly or indirectly to control lines.

While this creates 100's of extra corridors, the advantages make this technique far superior to the designer, and end user (client of contractor) than the current approach for the following reasons:

1) Templates are simple, easy to create, and have no complex display rules so they are functional for the novice user

2) The same template can be re-used 1000's of times, across any project, making the data consistent 100% of the time, giving reliable consistent symbology when the data is visualized

3) The consistent nature of common templates used always simpler digital quantities to be extracted, as similar objects can be collected by symbology

4) Changes are more manageable - change only the parts you need to change, and the connectivity of all the other corridors will automatically be adjusted

5) More than 1 user can work on the same road in the same section at the same time as everything is broken into smaller pieces

6) Simpler to train - for those unfamiliar with a 3D environment, this 3D Linear Method is identical to criteria

7) Processing is substantially reduced - it is quicker to process 100's of small corridors with no complex rules than 1 or 2 massive corridors with lots of display rules by a factor of 10.

This technique has been implemented across every designer I have worked directly with in Illinois over the past 4 years, and there has been 3 distinct reactions:

a) Those with some 3D knowledge embraced it fully, recognizing that this is the ONLY way to utilize the software, no exceptions

b) Those with minimal or zero 3D knowledge dismissed it entirely, citing "This is not the way Bentley teaches it"

c) Those with medium experience recognize its power, and use a toned down version of 3D Linear method - they build templates that span all lanes, 1 for shoulders, then 1 for end conditions, for example.

Overall it has been received positively from those who understand the software's limitations, and widely used across Illinois Tollway I-294 project currently underway.

This modeling technique has caused quite a controversy here from the State Government in Illinois (IDOT) due to the radically different approach. So I wanted to hear from the greater community regarding this technique.

If you would like to contact me directly about this, feel free to do so:

Alexander Badaoui, PE: P 312.467.0123 |

The presentation I made showing this in more detail is found here:

The attached PDF is a summary of the abstract presented.

This was geared towards a non-technical audience. The following power point below is more technically driven, detailing how the naming convention operates in Illinois:

Thanks in advance for your feedback on this technique.

  • It's a nice way of modeling, I have been thinking of doing a project this way.  In how many files do you break-up ex: a ramp?  One files with many corridor? or one file for the ramp main pavement then other file for the other parts?  I understand the big line it's more like whats the best way to structure the data or to generate reports on features if you have the same point repeated 2 times for each point.

  • The structure that seems to work the best is first to break up the project into design zones. Design zones are subjective, and based on a continuous geographical region of civil elements together. In the end, I break it up by bridges, North/South of major highways, or whole station cuts.

    The purpose behind the zone break down is data management. The larger the zone, the more processing, and the less people that can work at the same time.

    I create a central zone, ZONE-00. This zone will contain the following:

    1) Alignments - 1 DGN per major control line

    2) Super elevation - 1 DGN per control line

    3) Existing ground terrain model - 1 for the whole project

    The alignments/super elevation go in pairs. Reason - most likely these control lines will cross multiple zones, and their super development may happen across zones. So having them in a centralized location adds value.

    Now for the zone break down...

    In each civil design zone, there are AT LEAST the following files:

    1) Static corridors - 1 DGN that contains all corridors which do not need a terrain model (such as pavement, curbs, shoulders, etc).

    2) End condition corridors - 1 DGN that contains all corridors which require terrain models (such as grading corridors)

    3) Zone-specific alignments - curb returns, wing walls, etc, any alignment that will ONLY belong in 1 zone

    4) Surface templates - area surface templates for unusual non-linear sections, such as basins, islands, intersections, etc.

    5) Construction elements - corridors or other elements not necessary for the final product, but aid the design of other corridors.

    The corridors are based on the zone zero alignment/super files, and only extend within the limits of their design zone. 

    Therefore in answer to your question, a minimum of 7 DGN files at the bare bones. That assumes only 1 control line, and 1 design zone. Sometimes the zone DGN files are broken up even further. Smaller projects the super elevation and alignment files can be the same, but it makes the processing that much faster to separate them.

    Regarding reporting the same line in 2 different corridors, since the corridor name is pre-fixed to the point name, you construct consistent templates,  and if you follow a uniform convention, you will easily identify what data is repetitive or not.

  • I'm a 25+ year MX user from NZ.

    In changing to OpenRoads I got incredibly frustrated with exactly what you have eluded to is required when using a single template. Display rules, switches, having to update multiple templates that contain the same component, processing time, level of accuracy, going back to a template and trying to understand it months later, etc.

    As soon as I started solely using linear templates, that was it, it just didn't make sense to use a single template any longer. The simplicity and reduced processing time was immediately obvious.

    If you don't want to break it all the way down into individual components, somewhere in between works well and is how I like to operate.

    If you haven't tried it, you should, it really is that obvious, especially for new users

  • Thanks Noel! My background comes from MX Road in Australia, which was the inspiration behind 3D Linear Method in the first pace.

    Converting the corridors into 3D "strings" is the drive behind the technique, identical to MX Road.

  • Thanks a lot Alexander for your efforts, I have started looking at the videos you shared with me today, just a quick question floating my mind, when you are done with modeling, do you still recon the combined corridor model would be a dynamic one. for me the only unfortunate thing here is, most of my colleagues are inroads users (which is template based) and for them it is same even with OpenRoads.

    Looking forward to explore more.