This is where people underestimate the potential impact. Some ECV's can hit 5mph. The impact force of a moving object hitting a stationary object is F = (0.5 * m * v^2) ÷ d (where m is mass, v is velocity, and d is the distance the moving object will travel before it stops. Calculating d is another formula, so let's just say an ECV will travel 0.1m on collision before stopping, for the sake of argument. So for a 550lb ECV (250kg) and a velocity of 5mph (8 kph or 2.2 meters/sec) we get: F = (0.5 * 250 * 4.84) / 0.1, or 6,051 newtons, which is equivalent to 1360 pounds-force. Not a small amount of force.
If anyone is more versed in physics and math than I, please check my work.... I'm definitely not an expert here...