It appears Sisera was not in one of the lead chariots, and so is able to escape, even though his chariot is now immobilized in the pileup on the road immediately behind the battle area. Unable to reverse, and knowing that it is a matter of minutes before the Israelites swarm over his part of the column, like countless others he dismounts, clambers up the hillside and flees on foot.
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15 And the LORD routed Sisera and all his chariots and all his army before Barak by the edge of the sword. And Sisera got down from his chariot and fled away on foot.