A few things make me thing it's a much larger risk than 10e-16. 1. My numbers are on uniform distribution of planets. The milky way is not uniformly distribute

A few things make me thing it's a much larger risk than 10e-16. 1. My numbers are on uniform distribution of planets. The milky way is not uniformly distributed, and I suspect this isn't either. I hypothesis most of the planets will be on the spokes, just like most of the stars are. In addition, while it is 2kly tall, there is not a uniform distribution across the height. 2. Interstellar travel doesn't involves traveling a minimum of 4 lys, and a maximum distance without being intergalactic would be about 100,000lys. 3. Your assuming instantaneous travel across the light year. In reality we would consume at least 1 year in travel time, and likely much more. 4. The amount of resources it takes to build an intersellar ship is very large. The cost of a collision is high. This doesn't change the risk of a collision, but it does change what we consider acceptable risk.