The primary highways of Ecuador are designated with both a name and an alphanumeric designation. The highway designations begin with the letter E followed by a number on a shield that looks like the ones of the USA interstate highways.
If the highway is a trunk highway (travelling north to south), the number is odd. They are numbered from smallest to largest from the west to the east.
If the highway is a transverse highway (travelling east to west), the number is even. They are numbered from smallest to largest from the north to the south.