Thank you for your question. I look forward to working with you to provide you the information you are seeking for educational purposes only.
Actually, the law in Arkansas does not say they have to be visible to run radar and it also does not say they cannot park in a residential driveway to catch people violating the law by speeding
Arkansas DOES have a "speed trap law" and what it says is that under the Arkansas Speed Trap Law, A.C.A. § 12-8-401 et seq., it shall be presumed that a municipality is abusing police power upon a finding that:
The amount of revenue produced by fines
and costs from traffic law violations for which citations
were written by the police department of the affected municipality occurring on the affected highways
exceeds thirty percent (30%) of the affected municipality's total expenditures, less capital expenditures and debt service, in the preceding year.
A.C.A. § 12-8-403(b)(1). Once the prosecuting attorney of the judicial district in which the municipality is located makes the determination that the municipality is abusing its police powers, the prosecuting attorney has the power to issue the following sanctions:
(1) Order that a municipality abusing police power shall cease patrolling any or all affected highways; and
(2) Order that all or any part of future fines and court costs received from traffic law violations or misdemeanor
cases where the location of the offense is an affected highway shall be paid over to the county general fund of the county in which the municipality is located. See: A.C.A. § 12-8-404(a).
So in order to attack a speed trap in Arkansas you have to prove the above and it does not have to do with visibility as you stated.