I know what you mean. You call that motion blur. Its actually a bug with the tile layers alpha value. Well, Stefan once said its not a bug, I still think it is. Basically, what you do is change the alpha value of the default tile layer.
PHP Code:
//#CLIENTSIDE
function onCreated() {
tilelayers[0].alpha = .5;
player.gmap.tilelayers[0].alpha = .5;
}
It has to be set below 1 and above 0. How strong the motion blur is depends on the alpha value. Smaller = stronger.