I am assuming from your handle that you are located at Hong Kong. I am based at the U.S. and comparing from the U.S. that driving in Japan can be expensive due to price of gasoline, parking, and extensive toll roads.

If you are making half day or a day trip by car from Sapporo to Otaru you want to use toll road highway rather than surface road. Surface road will make driving time a lot longer and will cut into time you can spend at Otaru.

City parking lot at Otaru is JPY 300/20 min. Let’s say you are planning a day trip and ended up parking a car for total of 6 hours at various locations in Otaru, then that will be JPY 1800 total parking.

The highway connecting Sapporo and Otaru has a toll of JPY 1200 one way, which is JPY 2400 round trip. Again, taking a surface road will add driving time and provide less time at Otaru.

Currently, gasoline price in Sapporo is around JPY 155/liter (for those of us at the U.S. it turns out be $5.94/gal.). Round trip from Sapporo and Otaru is 76 km which ends up being JPY 589 for gasoline.

The total will be JPY 4789 for driving to Otaru, where four people round trip on train is JPY4960.

I have drove in Japan and driving in places like Tokyo, especially small narrow roads of suburb residential area is not comforting. Because of gasoline, parking, and toll roads, I never found driving a car by myself in Japan to be economical. As I showed above, if you have a group of four then finally able to bring up to breakeven point.

As for driving to Furano, it is faster to take northern route from Sapporo rather than take southern route. Toll on the expressway to Furano will be JYP 1250 one way, JYP 2500 round trip.