Cosmic Express: Why an Empty Carriage Won’t Pick Up Aliens

An empty carriage can still be unsuitable for its next passenger. If it has carried a green alien, the slime left behind prevents orange and purple aliens from using that carriage for the rest of that run. Dropping the green passenger off frees the seat, but does not make it clean again.

That restriction belongs to the individual carriage. A second clean carriage can still carry other passengers. Before replacing your whole route, identify which car passes the missed alien and what happened in that car earlier.

This guide concerns the original Cosmic Express, released in 2017, rather than Spooky Express. It explains ordinary passenger, carriage and slime interactions without giving a complete level solution. The current mobile build has not been play-tested here.

Keep track of two facts about each carriage

A carriage has room for one passenger at a time. That is separate from whether the seat has been slimed. The official Android description confirms the one-passenger capacity; later analysis of the game tracks occupancy and slime separately for each seat.

Use three simple labels while watching a route:

• Occupied: there is no spare place in that carriage for another alien.
• Empty and clean: an orange, purple or green alien can use it when the pickup conditions are otherwise satisfied.
• Empty and slimed: it can still carry green aliens, but not orange or purple ones.

The last state explains the apparent contradiction: you can see a vacant seat, yet the waiting passenger stays behind. The train is not necessarily broken, and a longer track will not repair the order in which that particular seat was used.

Occupancy and cleanliness are separate. These are conceptual states, not screenshots or a complete boarding test.

With one carriage, finish its non-green work first

If your only carriage carries green before a waiting purple alien, dropping the green alien home does not solve the problem. That purple alien still needs a clean seat, and you have already used your only one for green.

For a simple planning example, compare these event sequences:

• Fails for the later purple pickup: collect green, deliver green, then try to collect purple in the same carriage.
• Avoids that slime conflict: collect purple, deliver purple, then collect green.

These are ordering examples, not track solutions. You still need a legal route past the correct pickups, compatible homes and exit. But they tell you what to change: move the non-green service earlier in that carriage’s schedule, rather than repeatedly trying the same slimed pickup from another side.

The community hint guide’s single-carriage Delphinus example uses exactly this principle: finish the orange and purple deliveries before the green passengers.

With two carriages, “green last” is too broad

Do not treat the entire train as contaminated because one seat has carried green. Track the front and rear carriages separately.

Imagine carriage A has delivered a green passenger and is now empty but slimed. Carriage B has delivered a purple passenger and remains empty and clean. An orange passenger can still use B when B reaches a valid pickup position. A cannot take that orange passenger.

This is why a route can collect green before all the train’s orange deliveries are finished. The constraint is whether the remaining orange passengers can reach a clean carriage, not whether any green alien has ever boarded. The community hint guide explicitly allows an early green pickup with a second carriage kept available for orange.

Do not assume the game will rearrange passengers to make your plan work. Follow the actual carriage that becomes adjacent to each pickup. A clean seat elsewhere in the train is useful only if your route brings it to the passenger under the right conditions.

Example after both earlier passengers have been delivered. The route must still bring carriage B alongside the orange passenger.

An occupied seat can help you pass green safely

Sometimes you need to travel beside a green alien before you want to collect it. A carriage already carrying a passenger cannot take another one. Passing with a purple passenger aboard can therefore preserve that seat for the purple delivery instead of loading green too early. The community guide identifies this tactic in its single-carriage hints.

The limitation matters on longer trains: a full front carriage does not prove that a clean, empty rear carriage will also pass safely. Watch each car as it reaches the pickup. Ask what occupies it at that moment, rather than looking only at the first passenger aboard.

If the wrong car takes green, find the earlier drop-off or pickup that made that seat available. That event may be the real place to revise your route.

Clean and empty, but still no pickup?

Slime is only one reason an alien stays behind. Check two other possibilities before changing the passenger order.

First, check the passenger carriage’s position. Boarding depends on the carriage being beside the alien; the locomotive passing nearby is not enough to establish that an eligible seat reached it. Different cars reach the same location at different points in the journey.

Second, watch for two eligible aliens trying to enter the same empty carriage at once. In that situation, neither boards. This collision is described in the original review coverage and the community hints, and can be a deliberate way to pass a pair rather than a sign that the game is broken.

Do not turn that into “two nearby aliens always cancel each other.” They must actually compete for the same available carriage. A passenger that cannot use the seat is a different case from two eligible boarding attempts.

A surprising destination is a separate problem

If the alien boards successfully but enters the wrong one of two compatible homes, you have moved beyond a pickup problem. The developer explained in March 2017 that homes have a consistent priority and the passenger chooses the highest-priority unused option. The priority is not reliably apparent from the board.

Repeating the identical route is not a way to get a different random choice. Change the route or earlier deliveries so the unwanted destination is no longer an available competing option. Avoid assuming a universal left-side or right-side preference.

Watch the first event that differs from your plan

On your next attempt, count the carriages before starting and follow one of them through the troublesome section. Note its passenger and whether it has previously carried green.

1. Which carriage is beside the missed alien?
2. Is that carriage occupied, clean and empty, or slimed and empty?
3. Are two eligible aliens trying to use it simultaneously?
4. Did an earlier pickup or delivery put it in the wrong state?
5. Can you change that earlier event while preserving the remaining route?

A useful note is “rear carriage picked up green after dropping purple,” not just “orange refused the train.” The first describes a specific ordering problem you can work on without revealing the whole puzzle’s solution.

Sources and further reading