If you run when it is dark or poor visibility wear light clothing, wear a reflective strip and possibly wear a flashing light.
Be careful of cars approaching from behind (when you are running on the same side as the traffic). When you’re tired you tend to use your hearing rather than having to turn around. This means listening to music makes you less aware. However, if you hear a car approaching from behind, and move further off the road, be careful once it has passed of moving back to your former position, without looking, as often there is another car directly behind the first who is not expecting you to move suddenly back towards the road.
Being squashed should not be part of your training plan – rather be careful, especially when you get tired.