buying new sat nav help please.

[sut]

hi guys

i am looking for a little help if you dont mind please,
i have just started a delivery job and the company van has a inbuilt sat nav system that seems to work ok.

my issue is though that it does not have traffic management ( if thats the correct term )
i am looking to buy a cheap sat nav that i can run in conjunction with the works sat nav but use as the primary sat nav when it detects traffic issues so it will auto reroute me around traffic jams or slow moving traffic.

can anyone recommend a good cheap system please. I am happy with a second hand system if it brings the price down.

thank you
ant

[sut]

thanks for the info guys.

i have just downloaded waze i hope it good. my main concern is if it will auto reroute if bad traffic.