Police will generally not un-handcuff someone due to a panic attack in the US. It might be different than in Australia though.
In the US, if someone can not pay the full cost of a speeding ticket, the court can usually set up a payment plan. In the US, people get in trouble when they just try to ignore the ticket or don't notify the court of the financial difficulty.
In the US, people can't be arrested for debt alone - there are some strong laws that prohibit this unless someone commits fraud. This isn't always the case in other countries, and the regulations can be quite different than in the US. I am not sure what the laws are in Austrailia. However, it seems to be a very uncommon thing to arrest someone for debt alone. This might be a helpful site:
http://www.legalaid.nsw.gov.au/publ...d-resources/are-you-being-squeezed-for-a-debt
Failing to pay a speeding ticket could be another issue - but there seems to be help out there for that. Here is one site:
https://www.moneysmart.gov.au/manag.../trouble-with-debt/problems-paying-your-fines
If you are facing other possible legal charges besides the speeding ticket, consult an attorney. If the charges are low enough charges, sometimes a deal or plan can be worked out in advance where you can turn yourself in and get a citation/ticket/court summons instead of being arrested, or the PTSD can be explained by the attorney, and perhaps handled with a little more care.
In terms of the speeding ticket, it appears there might also be a Legal Aid system or organization that might be able to help people who otherwise can't afford an attorney.
It seems like there is a decent chance that by taking a few steps to begin to tackle this, you can avoid getting arrested. I hope you can find some outside help to get through it, and get greater support for dealing with the anxiety too. :hug: