Hello and thank you for your question.
Yes, there are no guarantees as to whether you will be simply released or granted bail or how soon you will appear before the court, though if you present yourself in the morning likely your will appear before the court the same day, though a full hearing of your case is unlikely to occur until later. Regardless, it will go much better for you if you hand yourself in rather than waiting to be arrested. However, in view of the following, I would recommend you go and see a lawyer immediately and hand yourself in at that time in the company of your lawyer because the offences in question are potentially very serious.
In terms of the penalty you face it will depend chiefly on what you did and what your driving record is like. The relevant offences are these:
If you were driving over 45kmph over the speed limit then that would be a circumstance of aggravation which means you could potentially be facing a term of imprisonment.
Only a fully briefed lawyer can give you a firm estimate of the applicable penalty, but the offences are certainly serious enough such that I would STRONGLY recommend you engage a lawyer to conduct your defence or, in the event you will be pleading guilty to attempt to either negotiate a lesser charge or cast your offence in the best possible light.
If you need assistance locating a suitable lawyer contact the Law Society of WA as they can refer you to a suitable lawyer.
However you proceed, I would not recommend giving a statement to the police until you have gone over your case in detail with a lawyer, as the police will likely try to pressure admissions out of you to assist them in securing a conviction.
I trust the above assists.
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