SELECT 
    jd.Name,
    ROUND((jd.Jam_count / totals.Total_jams) * 100, 2) AS Jam_percentage
FROM
(
    /* ---------------------------
       TRUE JAM COUNTS PER DEVICE
    --------------------------- */
    SELECT 
        Name,
        COUNT(*) AS Jam_count
    FROM
    (
        /* AREA JAMS */
        SELECT 
            Name,
            t_stamp
        FROM jam_area
        WHERE t_stamp BETWEEN :starttime AND :endtime

        UNION ALL

        /* DEVICE JAMS — EDGE DETECT */
        SELECT
            Name,
            t_stamp
        FROM
        (
            SELECT
                Name,
                t_stamp,
                Jam,
                IF(@lastName = Name, @prevJam, 0) AS prevJam,
                @prevJam := Jam,
                @lastName := Name
            FROM lane_data
                JOIN (SELECT @prevJam := 0, @lastName := '') AS vars
            WHERE t_stamp BETWEEN :starttime AND :endtime
            ORDER BY Name, t_stamp
        ) AS x
        WHERE Jam = 1 AND prevJam = 0

    ) AS all_jams
    GROUP BY Name
) AS jd

CROSS JOIN
(
    /* ---------------------------
       TOTAL JAM COUNT FOR PERCENT
    --------------------------- */
    SELECT 
        SUM(Jam_count) AS Total_jams
    FROM
    (
        /* repeat jam count block */
        SELECT 
            Name,
            COUNT(*) AS Jam_count
        FROM
        (
            /* AREA JAMS */
            SELECT 
                Name,
                t_stamp
            FROM jam_area
            WHERE t_stamp BETWEEN :starttime AND :endtime

            UNION ALL

            /* DEVICE JAMS — EDGE DETECT */
            SELECT
                Name,
                t_stamp
            FROM
            (
                SELECT
                    Name,
                    t_stamp,
                    Jam,
                    IF(@lastName2 = Name, @prevJam2, 0) AS prevJam,
                    @prevJam2 := Jam,
                    @lastName2 := Name
                FROM lane_data
                    JOIN (SELECT @prevJam2 := 0, @lastName2 := '') AS v2
                WHERE t_stamp BETWEEN :starttime AND :endtime
                ORDER BY Name, t_stamp
            ) AS x2
            WHERE Jam = 1 AND prevJam = 0

        ) AS all_jams2
        GROUP BY Name
    ) AS summed
) AS totals

ORDER BY Jam_percentage DESC;