The tourists are renting cars because your city isn't walkable and there's not enough public transit. If you added extra lanes for the tourists, then the locals would see all the empty lanes in winter and move deeper into the suburbs and drive more. Eventually the roads would be full in winter, and jammed in summer again. You need to build a train line to the airport and trams in the metro area.
Our cities are made to be walkable, it's Croatia after all.
But we have almost 0 public transport, especially between different cities, we only have train between 3 cities in the whole country and the train's go max 40km/h. Most of our cities are also small enough that you don't need any public transport inside of them cause everything that is in the cities is in the walkable distance ( I will explain later what the "is in cities" part means ), except the couple bigger ones that have buses that go every 20 mins to locations.
When it comes to buses also almost 0, tourists and even locals have to rely on buses for tourists that are controlled literally by other countries cause buses here barelly go. One good example is between 2 biggect cities here bus only goes to one then back to another at monday and friday, and only once in morning and once afternoon.
Worst part is that everything spread out across, if somebody here gets sick, he will have to travel to 3+ diff cities for diffeerent examinations each being 100+ km appart from each other + no public transportion unless the day you have the exam a bus is going otherwise you need to get someone to drive you there or have your own car. Same with buying literally anything other than just basic necesities.
What we have is complete lack of public transport and the fact everything is much spread out that it forces you into owning a car, or to get someone who can drive you, taxis also arent a thing here and are only found in couple big citiea, while being so expensive it's not worth it.
Edit: forgot to mention that most people here work and commute to job in different cities than what they live in, I had work in summer and had to commute 68km in one way each day for the work by my car because no public transport, reason being I was getting commute money from the job as compensation for having to use my personal venicle so it ended up being a lot cheaper than moving closer to the job. Even now searching for another job I still end up going for job intervies in cities 50+km away cause there is almost no job close to where I live and will most likelly commute to them again because it will be cheaper than moving there. I used me as an example but a lot of people that I know commute to their jobs by their car that are easilly 50+ km away,
Another good example was my hs english teacher, she traveled around 200km dailly one way to my hs cause it was cheaper than moving here with her 1 year old kid and working husband in her city of living.