How are other local govs managing speed limits in their road centerlines?

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08-18-2014 08:10 AM
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Regular Contributor II

We haven't been keeping a speed limit attribute in our centerlines but are looking to start doing so. The only way I can see to do so is the break the lines into segments at each speed limit change. That means managing the address ranges for a lot more segments now as we will have breaks in random places instead of just intersections. How is everyone else doing this?

 

edit: Moved to another forum in hopes of getting some more views.

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Regular Contributor

Try looking into Linear Referencing (dynamic segmentation). Going this route, you do not have to break your centerlines up to allow for various attributes.

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Regular Contributor II

What version of the LGIM is that from? The copy I downloaded on 7/23/14 doesn't have that domain in it. The release notes document that came with it jumps from November 2012 to the current 10.2 release so I don't know if that was dropped some time in the interim and wasn't listed as being dropped/

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Regular Contributor II

Well look at that. I must have gotten the last update somehow. Begs the question of which should be used for network analysis.

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Regular Contributor

Try looking into Linear Referencing (dynamic segmentation). Going this route, you do not have to break your centerlines up to allow for various attributes.

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If you are going the Linear Referencing approach you should also look at the Roads and Highways Extension.  If places a pair of date stamps on your Centerline network, which lets you retire historic alignments, but still maintain the historic events tied to the old alignments.  You use the time slider to expose events over different time ranges and you can set rules for how realignments, retirements, extensions, etc affect the route measures while the extension maintains measure synchronization for all registered event tables.  To cover a complete history, this is the approach I would recommend.

If you have ArcMap 10.2.2 they have added support for creating road segment events based on limit descriptions derived from any features that cross your roadways, including cross-street names, city boundaries, railroads, bridges, etc.  Either limit can include an offset distance along the road and a compass direction that defines the offset direction

Your address ranges do not need to change with LR when events simply divide an existing Centerline segment, since LR uses measure positions to segment the road rather than line splits.  All LR events can be combined together with LR tools without the problems of other overlay techniques, because they only overlay on the route they are connected to and the events will not overbound their limits.  LR events are tied directly to the route Centerline geometry, but can be displayed with a side offset to the correct side of the road for each DOT of a speed limit if they are created as separate Roads and Highways event records.  Alternatively you can create a single event for the speed limit with separate fields for Left and Right speeds and offsets, and after extracting the data to a non-Roads and Highways standalone table you can create two event layers (one layer for each DOT) to display the one record with offsets for each DOT.

If you are going to divide your actual Centerlines with address ranges I recommend you look at the Address Management Add-In and Attribute Assistant Add-In that can be downloaded from here.  This add-in adds a Create Road and Split Intersecting Road construction tool that will divide address ranges proportionally where a newly created line crosses an existing Centerline with address range data.  For splits that do not involve a new centerline I create a dummy centerline to create the split and then delete that dummy centerline.  You can modify a configuration file to use your own Centerline schema rather than the Local Government schema if you want to.

Attribute Assistant can be modified to perform many other automations that you can configure for maintaining any of your data.  It can automatically perform autonumbering with unique values, look ups, validations, field calculations, spatial joins, etc. as you edit your features after you have created the correct rules in the DynamicValues table.

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Regular Contributor II

Chris, I use Linear Referencing to track and manage Speed Limits on our system.

That said, we do have issues on defining the "Speed Zone" that is related to the posted sign(linear extent).  I have not yet found any definitive way to interpret the start or end of a speed zone for which a speed limit sign is referencing. This becomes tricky when you have ramps and have acceleration and deceleration lanes involved.  Since I could not find any rules defining the start and end of the speed zone; they are judged by hand or eye in our shop and reviewed by traffic engineers (This is very inefficient).

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