Basking turtles... of all kinds... do so in response to light. Outdoors this is not a problem; the light is (surprise!) just exactly the correct intensity for them. And the water always stays cooler than the air, so, even if there's no breeze, they can slip into the water to prevent overheating.
In an artificial environment things are different. It's difficult to get light that's the intensity of sunlight (or even close to it) without overheating the tank, water, and everything else. This problem can sometimes be partially solved by having the tank light very close to the turtles (the phrase "a 40 watt bulb 6 inches away" comes to my memory but you should check on that), so you have a "basking spot." But that works best if the tank is very large and, thus, would have some cooler spots in it, away from the light.
In a small tank... it's just very tough to do.
And, yes, if I was almost killed crossing the road, I might want to be cautious for awhile, too.