Something

#define MAX_CARS 255


new SampleData[MAX_CARS];
for (new i; i<=MAX_CARS; i++)
{
  SampleData[i] = 1;
  // in this case, things would go badly because the last key in SampleData is 254!
}
//
// vs:
//
new SampleData[MAX_CARS+1];
for (new i; i<=MAX_CARS; i++)
{
  SampleData[i] = 1;
  // we now have a valid SampleData[255]
}