Want to build a new Network

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05-16-2012 06:31 AM
JeffreyTippen
New Contributor
Hello everyone,

I work for a organization who uses a very labor intensive routing program for school district transprotation routing.  I would like to switch over to ESRI solution using Network Analsyt.  Our district services approx 65,000 students of which about half require transportation to 67 schools.  We have a fleet of about 400+ buses.  We keep growing and have out grown our current process.

I do have many off and on years of ArcGIS expeirience but mostly on single workstation.

I guess my beginning questions would be on reccomended reference materials so I can approach this the right way.  I will have to create a test network to demonstrate the capability and advantages of a geodatabase  to support not only the Transportation group but other divisions within the district.

I would appreciate any advice from current users of the best approach I should take.  Since I'm starting from scratch I would like to stay on tract.

Thanks in advance for your time

Jeff
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12 Replies
PatrickStevens
Esri Contributor
You should be able to use them as barriers with some sort of impedance value.  An alternative is creating turns, and they can get ugly...


Barriers can be a viable solution, but I would recommend using your stop light points as a junction source in the network.  Be sure that your stop light junctions are coincident with the source junctions for the affected intersections.

Once the new junction source is built into your network, there are a couple of options on how to set the delays.  If you have one generic value for the delay at every light (say 5 seconds), then use a constant evaulator on that junction source with a value of 5.  If you have different delays for each light, then set up a field on your new junction source (say "Delay"), then use a field evaluator that reads the Delay value in.

Constant evaluators are the fastest of the evaluators, as the value is set.  Field evaluators are next fastest, as the values are processed when the network is built, not dynamically as the solve occurs.

The caveat with this implementation is that your stop light delay will be incurred no matter what the maneuver at the intersection is.  A left turn, a right turn, a U-turn, and driving straight through the intersection will incure the same delay coming from every direction that passes over the new junction.

That same caveat would apply for the point barrier implementation as well, though.  Turns are the most accurate solution, as they give you more refined control, but as you know, there can be A LOT of turns to digitize.

Another potential solution is the Global Turn Delay Evaluator (GTDE).  If, as dicussed previously, you have a generic set of delays depending on the type of maneuver, you can use this evaluator to specify them.  The GTDE works based on type of turn (straight, left, right, u), as well as road designations (local, secondary, major).  Your level of control can be as fine as a specific, generic delay for every left turn from a local road onto a major road, for example.
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JeffreyTippen
New Contributor
OK,

I'm working on the best way to handle stop signs.

I have another question that I have been putting off.  In addition to our normal bus fleet we have about 100+ special needs buses.  I was planning the network to prevent the regular buses from turning onto cul-de-sac streets or others that would be difficult to turn around on.  Since our special needs buses are shorter they can enter and turn around in cul-de-sac streets.

My question is:  Do I need a separate network for special needs over the district?

Or is there a way to code the bus to allow it to enter cul-de-sac or dead end streets using the normal street network?

I hope I'm clear on this.  I know I will be asked alot of questions regarding special needs routing.

Thanks in advance,

Jeff
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PatrickStevens
Esri Contributor
In addition to our normal bus fleet we have about 100+ special needs buses.  I was planning the network to prevent the regular buses from turning onto cul-de-sac streets or others that would be difficult to turn around on.  Since our special needs buses are shorter they can enter and turn around in cul-de-sac streets.

My question is:  Do I need a separate network for special needs over the district?

Or is there a way to code the bus to allow it to enter cul-de-sac or dead end streets using the normal street network?


You are working with what we call the "U-Turn Policy".  There are 2 places where you can adjust u-turns.  Here's a link to the help topic about it.  You do not have to make changes to your network to use either of the properties.

The first concept is called "Curb Approach".  This will set how the vehicle approaches its stops.  Should the vehicle arrive on the same side as the stop?  And can the vehicle make a u-turn when it leaves the stops? 

The second concept is called "U-Turns at Junctions".  This option governs how the vehicle behaves when traveling between stops.  When the shortest path includes making a u-turn at an intersection or at a dead-end, can my vehicle handle this type of maneuver?

Curb Approach is set in the properties of the stop itself.  U-Turns at Junctions is in the analysis settings for any of the solvers you might use.
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