I have used Book 2 Park in the past for Reagan National with a positive experience. This is the 1st time I have used it for BWI parking. Although it is outdoor parking, I felt that my car would be safe at this site. The Shuttle was right on time, and the driver was very pleasant. The airport was only minutes away. The hotel agent at the desk was very accommodating. I would have given it a 5, except that instructions where to park turned out to be not clear. I saw that the parking lot appeared to be full, and I went back to ask where specifically to park. I was told to park along side of the building. There was only one spot available. When I returned from my trip, I had a note on the car, stating that particular spot was not a designated parking spot, and there was an overflow lot to park in. I was not aware of an overflow lot, and was not told about this lot, when given instructions. It would have been helpful to have had clarity. It makes for a more seamless transition, at an already stressful time, when catching a flight.