The **maximum blood alcohol concentration allowed** for drivers in general is **0.5 grams per liter**. This measure refers to the amount of alcohol present in each liter of a person's blood after consuming alcoholic beverages.

- For drivers who are not in special situations, such as those who have had their driving license for less than two years or who drive special transport vehicles, the allowed rate is **0.5 grams per liter of blood**. This is different from the measurement in exhaled air, which is **0.25 milligrams per liter** for these same drivers.

- It is important to remember that, although these are the legally permitted rates, the only completely safe rate for driving is **0.0**, that is, not having consumed any alcohol at all. This is because alcohol affects driving ability and increases the risk of accidents.

- The blood alcohol concentration can vary according to several personal factors, such as weight, sex, the amount and type of alcohol consumed, and the time elapsed since consumption. Therefore, it is crucial to be aware of these factors and avoid driving if alcohol has been consumed.

In summary, for most drivers, the maximum allowed rate is **0.5 grams per liter of blood**, which corresponds to **Answer 1**.