Illustrative route lines through real stops, not to scale. Christchurch to Arthur's Pass, and Christchurch via Hanmer Springs to Lewis Pass.
Two roads cross the Southern Alps between Canterbury and the West Coast: SH73 over Arthur's Pass, and SH7 over Lewis Pass via Waipara and Hanmer Springs. Both are managed under the same alpine open and closed protocol NZTA has run on Lewis Pass since 2017, later extended to Arthur's Pass, because both routes are genuinely weather-vulnerable in winter. It's rare for both to close at the same time, which is the practical reason to know the alternative exists before you commit to a route. This page treats the crossing as the trip in itself, whether that's a straightforward one to two day crossing or the core of a longer three to five day loop paired with a West Coast or Hanmer Springs leg. For the Hanmer Springs side of that pairing, see the Hanmer Springs Mixtape, which isn't repeated here.
The two roads: SH73 and SH7
Christchurch to Arthur's Pass Village on SH73 is about 154km and takes roughly 1 hour 50 minutes, climbing to a summit of 920m through beech forest and subalpine country. Christchurch to the Lewis Pass summit on SH7 is a longer run at around 188km and about 2 hours 20 minutes, via Waipara and Hanmer Springs, climbing to 864m, one of only three road crossings of the Southern Alps. Hanmer Springs itself sits just off SH7 on the short SH7A spur, about 133km and roughly two hours from Christchurch, and makes a natural stop or overnight on the Lewis Pass side of the crossing (AA time and distance calculator figures throughout). Neither road is faster than the other by any meaningful margin: the real planning question isn't which pass is quicker, it's which one is actually open on the day you want to cross.
Skip a same-day round trip through either pass in winter without checking both ways
NZTA has run an open and closed alpine management regime on Lewis Pass since 2017, later applying the same approach to Arthur's Pass, closing the road outright in poor conditions rather than allowing slow, unsafe travel through snow and ice. NZTA's own clarification notes it's rare for both passes to close simultaneously, but "rare" isn't "never," and a pass that's clear in the morning can close by afternoon once weather moves in, which is exactly the pattern that catches out a same-day there-and-back attempt. The road can be open when you drive west in the morning and closed by the time you'd planned to drive back, leaving you on the wrong side of the Alps rather than home for dinner. Check NZTA's Journey Planner highway conditions page before you leave, and check it again before you start the return leg, not just once at the start of the day. Arthur's Pass Village itself is tiny, a permanent population of around 48 people according to Selwyn District Council, so an unplanned overnight there isn't a given fallback with unlimited rooms to spare.
Arthur's Pass has an alternative to driving: the TranzAlpine
Arthur's Pass has an option Lewis Pass doesn't: the TranzAlpine scenic train, a roughly five-hour journey between Christchurch and Greymouth that crosses the same alpine divide by rail, on viaducts and through tunnels the road doesn't use. It's a genuine alternative for the Arthur's Pass side of a crossing, not just a novelty add-on: some travellers take the train one way and a rental car the other, which avoids the weather-dependent driving on at least one leg. Lewis Pass has no equivalent rail option, so SH7 is a road-only crossing regardless of conditions, which is worth knowing if the driving itself, rather than just reaching the coast, is what you're trying to avoid on a bad-weather day.
Treat this as a one-way through-route to the West Coast rather than a there-and-back day trip from Christchurch, and check NZTA's alpine status for both passes before you leave, not just the one you're planning to drive.
The bit nobody publishes: a one-way crossing usually means a one-way rental car, and standard NZ rental firms often charge a relocation fee for dropping a vehicle at a different depot to where you picked it up, on top of the usual daily rate. Some operators build it into the headline quote and some add it separately, so it's worth confirming which before you book, rather than discovering it at the counter. Pairing the TranzAlpine one way with a rental car the other avoids a same-day weather gamble on Arthur's Pass, but it doesn't avoid this cost, it just moves it from fuel and time to a line item on the rental agreement.
This crossing is worth building a trip around if you treat it as a one-way leg of a longer loop, whether that's continuing to the West Coast or looping back via Hanmer Springs, and if you check conditions on both passes before committing to either. It's not worth attempting as a same-day round trip in winter without checking the return leg separately, since the closure risk runs both ways, not just on the drive out. If Hanmer Springs is part of the plan, see the Hanmer Springs Mixtape for the detail on that leg rather than treating it as a quick roadside stop.
Which pass is more reliable in winter, Lewis or Arthur's?
Neither, consistently. NZTA runs the same open and closed alpine management on both SH7 and SH73, and it's rare for both to close at the same time, but that's not a guarantee either will be open on a given day. Check NZTA's Journey Planner highway conditions page on the day rather than assuming either pass is automatically the safer bet.
Can I do this as a day trip from Christchurch?
Only as a one-way through-route to the West Coast, generally. A there-and-back day trip through either pass is technically possible given the drive times involved, but it leaves little real time at either end and carries the closure risk on both legs, not just one. Most people treat the crossing as one leg of a longer loop rather than a same-day return journey.