If you're taxed at source (Quellensteuer), you can't

If you file a tax return, you can, if you can prove one of the following:
- The distance from your home to the nearest public transport stop (or work to nearest stop) is more than 1 km
- The total time spent commuting per day is more than 2 hours 30 min
- You need your car for work-related and/or medical reasons
If any of these are true, you can deduct up to 0.65 CHF/km, so if you have a 20 km commute (each way, as in my case), you could deduct:
20 x 2 x 220 (max. working days allowed/year) x 0.65 = 5720 CHF
And yes, I live in BL as well