99942 Apophis is an asteroid that will make a close pass to Earth in 2029. There is no danger of a collision. If — I repeat, if — it passes through a very tiny window in its trajectory in 2029, it could have around a 1 in 250,000 chance of striking our planet during its next pass in April 2036.
1 in 250,000 is almost sure to not happen. In the unlikely event that there is an impact, however, the devastation will be regional, and people in the affected area will have ample warning to evacuate. After all, we're tracking the thing now, so there's no worry about a surprise event when it's close.
Near-earth objects pass by us all the time, and there are collisions all the time. Most of them, however, are too small to even notice. You can visit NASA's tracking program site here, and also check out SpaceWeather.com. We are in no danger of any major collision at this time. Apophis, as I mentioned above, is a tiny concern in 2036, but even in a worst-case scenario people will have ample warning to get out of the way.
