Why are travel times different across Apple Watch and iPhone?

For those that user ETA across both iPhone and ETA might notice travel times differ slightly in what is reported. The reason is that the Apple Watch and iPhone app use different sources for data. The iPhone uses data from Apple Maps, the Apple Watch uses data from HERE Maps. 

The reason for the difference is simply to help us provide a very fast and responsive Apple Watch app. To use Apple Maps on the watch it required the app to communicate with your iPhone to get data information. It sadly was slow and unreliable. With the new Apple Watch app launched in 2021 we partnered with HERE maps to use their API and data services. It allows us an independent app that is dependable, fast and updates very regularly.

In our tests HERE Maps and Apple Maps report very similar travel times, often differing by only a few minutes.