The organisers usually arrange parking at several locations close to the stadium (tennis club, school, shopping centre car park). Specific info will be on this page https://www.speedwaygp.com/son/event/2020-Final under 'Event Info' nearer the time.
Unfortunately I arrived late last year and was forced to park on a nearby street. Having just parked the car I was met by a local resident who asked if I was attending the speedway and then threatened that if I didn't move my car within the next five minutes he would slash my tyres - charming, eh !
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