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I have four points representing harbors along the coast. I also have a roads layer that has info on each road segment such as length, speed limit, and travel time.

I calculated travel time with [(length in miles) / (speed limit in mph)] * 60 for the time it takes to traverse each road segment in minutes.

What I want to do now is: Work out from each harbor point along the road networks to get the total travel time to the nearest harbor for each road segment. All the tools I've found that do something similar to this require both a start and end point. Is there a way to do this without turning each road segment into a point itself?

Any help is appreciated, thank you.

P.S. To better visualize my end goal, I essentially want a sort of "Euclidean Distance" effect, except it needs to stay along the roads layer and will total in time rather than meters/miles/etc.

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What software are you working in? –  Ryan Garnett Apr 14 '13 at 20:21
    
@RyanGarnett I'm doing this in ArcMap10 with most of the extensions/add-ons. –  Michael Apr 14 '13 at 21:01
    
Couldn't you use Network Analyst. If you made the harbours as a point, then you would have your Start and End points. You may need to snap the points to the line segments. This may not be what you want to do, but it will give you the results. Sort of "making it fit" to the requirements, you would need to manually select the road segments for each part of the trip, dissolve them and then do the calculations. –  Ryan Garnett Apr 15 '13 at 6:19
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2 Answers

You might take a look at the Closest Facility solver of Network Analyst. Then each harbour will become a facility and three others - incidents. Then you would do the opposite for each harbour - another one will become a incident, others - facilities and so on. I doubt you need ModelBuilder or Python here - since you have just four points. Then you can aggregate the travel time taken for every road segment along the routes between harbour points. I would suggest taking a look at an add-in which makes it possible to convert the result routes into a feature class (with edges, turns, junctions) which you may use for further geoprocessing.

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Using Network Analyst extension, you could:

1 - Use OD Matrix analysis, with the 4 harbor points, using travel time as cost, to calculate "nearest" facilities from each other;

2 - Select the 3 "nearest" pairs of harbors;

3 - For each of the pairs, use route analysis to create best route between them.

4 - Dissolve resulting lines summing the time;

Note: If your road network has oneways, going from harbor 1 to harbor 2, might be different from going from harbor 2 to harbor 1

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