Route optimization not using all vehicles to minimize objective

Directions API Route Optimization API
1

Hi,

We have found an optimization request that produces a very poor result, but it is not clear why. There are 25 identical vehicles, there are no allowed_vehicles and no time windows. However for some reason the optimization refuses to use most of the vehicles and only assigns routes to 9 of them, when using:

[{
    "type": "min-max",
    "value": "completion_time"
}]

as the objective. The max completion route in the result is 36476.

However if the objective is changed to

[{
    "type": "min-max",
    "value": "completion_time"
},{
    "type": "min-max",
    "value": "activities"
}]

Then it creates routes for 24 vehicles and has a max completion time of 20454. I’m not sure why changing the objective improves the result, as if it was possible to minimize the max completion time by using more vehicles then I’d expect the optimization with just min-max: completion_time to do it too.

I’ve attached the optimization request body.

request.txt (143.0 KB)