Let me break this down for you ..
You work out how you’re getting to your destination in advance and buy any travel tickets needed using internet. If you want, you can check for major delays, diversions, road closures using a mapping app like Google maps, or RAC/AA/ National Highways websites.
Then once you’re underway, use said mapping app, or satnav. Phone data bolt ons are cheap so buy one from your provider if you don’t have enough data in your plan.
Navigation apps still continue to work in most of the UK even where the 4g signal is poor, provided you don’t change the route. But you can come unstuck with this in some remote / mountainous areas, or abroad, so still know the rough route you’re taking.
Your car radio has a feature called Traffic Announcement. TA is an automatic traffic bulletin alert system. Radio stations that broadcast travel updates set a TA flag (a digital signal) in the FM broadcast. When a traffic bulletin starts, your radio interrupts whatever you’re listening to (Spotify, etc. switches to the station broadcasting the announcement then returns to your previous audio afterwards. It should inform if a road near where you’re driving is closed due to an accident, or there’s a diversion, it’s another way to find out information that isn’t dependent on internet signal. It comes through the FM radio signal. So you can listen to Spotify and still use it.