The **maximum permitted blood alcohol level** for a school transport vehicle driver is **0.15 milligrams per liter of exhaled air**. This is because vehicles transporting minors, such as school transport vehicles, have stricter restrictions regarding the amount of alcohol allowed in the driver's system.

- Blood alcohol concentration is measured in milligrams of alcohol per liter of exhaled air. For drivers of vehicles transporting minors, the permitted level is **0.15 milligrams per liter of air**.

- This restriction is lower than that for other drivers, who have a limit of **0.25 milligrams per liter of air**. The reason is that drivers of vehicles transporting minors must ensure maximum safety.

- Additionally, driving with a blood alcohol level above the permitted limit can result in severe penalties, such as fines or even the loss of points on the driving license. For professional drivers and those with less than two years of experience, penalties start at a level of **0.15 milligrams per liter of air**.

Therefore, it is crucial that school transport drivers maintain a blood alcohol level of **0.15 milligrams per liter of exhaled air** or less to comply with regulations and ensure the safety of passengers.