What are considered serious driving convictions ?

I am looking to drive under motability for my gran as a named driver , however on the sight it says you may be denied if you have any serious driving convictions .In February 2011 I got caught with a red light camera accidently running a red . I was wonmdering if this would stop me getting motability or if this is a minor offence. I am 17 ,18 in august and i have been driving since january . If anyone knows if this would affect me any info would be appriciated.