"Radio offers the greatest proximity to shopping occasions".
Well it must work to some extent. Their advertising worked on you. I do think a lot of those statistics are their PR to try and sell their services. I get promotional material from a lot of magazines trying to sell their services. Everyone of them puts out data showing they have the most reach in a market.
As far as the part about reaching them within a half hour of shopping. Is that really when we would want to reach them? If they are driving to the mall or the grocery store their mind is on clothes and food not having their lawn cut.
I have no experience with radio advertising but do have a lot in other forms of advertising. The only direct experience I have with radio is being a guest on a program on our local and most listened to radio station which produced one call for a service I don't provide.
Personally for services like we provide I would rate a good website the best option. Good graphics on trucks and vehicles as another top choice and a few others options ahead of radio. I could be wrong and if you have tried it and had good results I am sure we would all like to hear about it.