The LEDs may be a battery level or assistance level indicator. If there is varying assistance levels, there will be a control for those somewhere. Some of the cheaper ebikes only have one level. Assuming the bike is road legal or close to it, there's no reason why you should crash it. The motor won't be particularly pokey and should cut out when you stop pedalling or brake. Ebikes are heavy lumps, probably more chance of it toppling over when you come to rest or try to restart.