public function units($units, $string = false)
    {
        // Explode units
        list($distUnit, $timeUnit) = static::explUnits($units);

        // Get and format the distance and time unit values
        $distVal = $this->dist->unit($distUnit);
        $timeVal = $this->time->{$timeUnit};
        $distVal = number_format($distVal, 99, '.', '');
        $timeVal = number_format($timeVal, 99, '.', '');

        // Calculate the velocity value
        $velocity = bcdiv($distVal, $timeVal, 999);
        $velocity = static::removeTrailingZeros($velocity);

        // Return either string or double
        return $string ? $velocity : (double)$velocity;
    }