If you have held your driver's license for one and a half years, what is the maximum blood alcohol level allowed for driving?

Correct answer: 0.3 grams per liter of blood.

After a year and a half with your license, you are still within the first two years, so the lower limit applies to you. If you are an adult, you must not exceed 0.3 g/l in blood or 0.15 mg/l in breath. The limit of 0.5 g/l applies once you reach two years, and 0.25 is the general breath alcohol limit in mg/l, not the blood alcohol limit.

Real Decreto 1428/2003, de 21 de noviembre, por el que se aprueba el Reglamento General de Circulación