Exercise 3 solution (Python)

def to_min(t):
    h, m = t.split(":")
    return int(h) * 60 + int(m)

def to_clock(mins):
    return f"{mins // 60:02d}:{mins % 60:02d}"

def naismith(dist_km, ascent_m):
    return round(dist_km * 12 + ascent_m / 100 * 10)

def route_card(legs, start, escape):
    clock = to_min(start)
    print("From      To        Dist   Ascent  Time  Arrive  Escape")
    for name_a, name_b, dist, ascent in legs:
        mins = naismith(dist, ascent)
        clock += mins
        print(f"{name_a:<9} {name_b:<9} {dist:4.1f}   {ascent:5d}   {mins:4d}  {to_clock(clock)}   {escape[name_b]}")

legs = [("Start", "Bridge", 2.0, 0), ("Bridge", "Col", 3.0, 350), ("Col", "Summit", 2.9, 330)]
escape = {"Bridge": "back to road", "Col": "south track", "Summit": "retrace to Col"}
route_card(legs, "09:00", escape)

Output:
From      To        Dist   Ascent  Time  Arrive  Escape
Start     Bridge     2.0       0    24  09:24   back to road
Bridge    Col        3.0     350    71  10:35   south track
Col       Summit     2.9     330    68  11:43   retrace to Col

The clock variable carries the arrival time forward from leg to leg, so each row shows when you should reach that point. On the day, write your actual arrival beside each planned one: if you are falling behind, the escape column tells you what to do about it.