I went to Panama for work several times back in the 90s with a guy who had been there before and all over Central America and Northern Africa. He always took a few extra 20s in his pockets. The traffic cops would pick us out, even though we were following a line of cars. They would tell us about some traffic law like "no cross the double amarillo line". He'd ask "warning, por fa vor". If the hesitated he'd say it again with a $20 in his hand. We'd drive away every time. He just considered it part of the cost of doing business there.