http://revach.net/article.php?id=2731

Section: Taryag Mitzvos   Category: Taamei Hamitzvos
Parshas Shoftim: Moreh Nevuchim - It Is All Part Of The Hunt

The Rambam in Moreh Nevuchim (3:40) says that the reason for the whole procedure of the Egla Arufa is to make our roads safe, reveal the killer, and remove him from our midst. Therefore explains the Rambam, we make a drawn out ceremony so that all the neighboring townspeople come out with the Zekeinim and declare that they don't know the murderer and that they are not harboring a criminal in their midst. This ceremony will make them realize how bad an aveira it is. Then if they do know something, they will come forward.

Another benefit says the Rambam, is to cause a commotion and get the people talking. Maybe through this, clues will emerge that will lead to the killer.

Lastly says the Rambam, by forbidding planting ever again in the field where the Arifa is done, you can be assured that the owner of the field will do everything in his power to find the person who committed the murder and save his property.