A state highway to be known as state route number 171 is established as follows:
Beginning at a junction with state route number 90 west of Moses Lake, thence northeasterly by way of Moses Lake to a junction with state route number 28 in the vicinity west of Odessa. Until such time as state route number 171 is actually constructed on the location adopted by the department, no existing county roads may be maintained or improved by the department as a temporary route of state route number 171.