At first glance, the scene looks like a chaotic traffic jam where every car is stuck because of another. Each vehicle is either directly blocked in front or indirectly trapped due to limited maneuvering space. However, not all cars play the same role in this gridlock.

Some are “locked,” meaning they cannot move at all, while others are “key blockers,” meaning their movement will immediately create space for multiple cars.

Let’s examine the situation logically and precisely.

Car 1 (white car at the top right) cannot move backward because it is directly blocked by car 4. Moving forward is also not an option due to the curb and limited space. Therefore, car 1 is completely dependent on car 4.

Car 2 (yellow car) is tightly pressed between car 4 and car 6. It cannot reverse because car 7 is behind it, and it cannot move forward because car 4 is in the way. This makes car 2 fully trapped unless car 4 moves.

Car 3 (red car) is blocked in multiple directions. It cannot reverse because car 6 is behind it, and it cannot move forward because car 4 is partially obstructing its path. Again, car 4 is a critical factor here.

Car 5 (orange car) is stuck behind car 3. Even if it tries to reverse, its angle and proximity to the curb make it ineffective in solving the overall problem. It does not influence the rest of the cars significantly.

Car 6 (green car) is in a central position but is boxed in by cars 2, 3, and 7. It cannot move in any direction unless one of those cars moves first. However, none of those cars can move unless car 4 creates space.

Car 7 (purple car) is blocked by car 6 in front and cannot maneuver backward effectively due to limited space. It is also dependent on the central cluster being unlocked.

Now we arrive at car 4 (blue car), which is the key to everything.

Car 4 is positioned at an angle where, unlike the others, it actually has clear space behind it. This is the crucial detail. While every other car is tightly blocked either front or back, car 4 has just enough room to reverse without immediately colliding with another vehicle.

When car 4 moves backward, several important things happen at once:

First, it frees up the front space for car 2. This allows car 2 to move forward or adjust its position, relieving pressure in that section.

Second, it removes the obstruction in front of car 3. Once car 4 is no longer blocking it, car 3 gains the ability to move forward or reposition, which in turn affects car 5.

Third, it creates breathing room in the center of the cluster, allowing car 6 to potentially maneuver once cars 2 and 3 shift.

Fourth, it indirectly frees car 1, which was previously blocked by car 4. Once car 4 reverses, car 1 can move forward and exit the congestion.

This single movement—car 4 reversing—initiates a chain reaction. Unlike other cars, which would only create minor or isolated changes, car 4’s movement impacts multiple vehicles simultaneously. It is the only car whose motion reduces overall congestion rather than shifting the problem elsewhere.

The key reason behind this is positioning. Car 4 sits at a central junction where it connects several blocking relationships. It is not just another trapped car; it is the pivot point of the entire gridlock.

In puzzles like this, the solution is never about random movement. It is about identifying the one element whose change creates the greatest impact. Car 4 is that element because it is the only car that is both movable and strategically influential.

The correct answer is: Car number 4.

To understand why car 4 is the only vehicle that can solve the entire situation when put in reverse, you need to carefully observe the positions, angles, and dependencies between all the cars in the image. This is not just about which car has space to move, but which movement actually breaks the chain of blockage affecting all the others.

In conclusion, putting car number 4 in reverse solves the problem because it is the only vehicle with enough space to move and the only one whose movement unlocks multiple other cars at once. Its position allows it to break the chain of blockage, creating a cascading effect that eventually frees the entire traffic jam.