Smoking while driving **can decrease the driver's level of attention**, which increases the risk of accidents. Here is why:

- **Distraction**: When searching for and lighting a cigarette, the driver diverts their attention from the road. This means they are not fully focused on what is happening around them, which can lead to dangerous situations.

- **Occupied hands**: Holding a cigarette means that one hand is not available to handle the steering wheel, which can hinder the ability to react quickly to any unforeseen event.

- **Reduced visibility**: Cigarette smoke can obstruct the driver's view, making it more difficult to clearly see the road and surroundings.

- **Air quality**: Smoking inside the vehicle deteriorates the air quality, which can affect the driver's cognitive and physical abilities, decreasing their attention and reflexes.

In summary, smoking while driving introduces several distractions and obstacles that can significantly reduce the driver's attention, increasing the risk of accidents.