# Solve for alternate routes without barriers or additional stops in ArcGIS Network Analyst?

I created a network dataset using ArcGIS Network Analyst. I have one start and one destination point. I want to find the three shortest paths from start to my destination (find three shortest paths from point a to point b). Is it possible to run an analysis for three different routes?

• I'm not sure I understand your question. All things being equal (no barriers, etc.) there should only be one shortest route between two points in a network. Are you saying you have three different starts and destinations? Or you want three alternate routes? Three alternate routes would be difficult without a specific barrier, because there would be a number of alternates (one block out of your way and back anywhere on the route). Nov 26, 2014 at 22:26
• Thanks @ChrisW . I have one start and one destination. I want three alternate routes. Nov 27, 2014 at 6:09
• I agree with Chris, you need some kind of additional information in order to define what your alternate route should be. Those could be barrier, additionnal stop, time dependent impedance...Alternatively, you can compute the sum of the isochrones around your start and your destination, which will give you a zone of least cost (corridor), but the number of routes in the corridor is then undefined. Jan 15, 2015 at 13:08

## 2 Answers

As far as I know it's not possible to solve for alternate routes without some additional input or change to the analysis. In a network, given a particular impedance, there is only one shortest route between two points. As soon as you start looking for alternates without any additional input you've essentially removed the 'shortest' constraint and are back to a potentially large number of paths between any two points. Even keeping it to 'next shortest' would pretty much be going one block over, one block parallel, and one block back to your original route - anywhere along it.

In order to look for an alternate route you'd need additional criteria - barriers introduced along the original route, an additional stop, different impedance (maybe length is different than drive time because of speed limits), or some analysis restriction (like avoid toll roads or highways or something).

Also, look under the advanced settings tab.

There, you can set the importance of Time-Window Violations, which can increase or decrease travel time depending on your choice, whether you want to reach locations on time, or service more locations within the time frame.

There is also an Excess Transit Time, set to high, the solver tries to find a solution with less excess transit time between paired orders at the expense of increasing the overall travel costs. Set to low, the solver tries to find a solution that minimizes overall solution cost, regardless of excess transit time.

Hope this offers some insight

• There is no advanced setting tab for "new route ".It's accessible in "new location allocation" Jan 17, 2015 at 4:57