Turnouts, the technical term for what are commonly called switches, have a normal and reverse directions. Usually, "normal" is the "straight" route and "reverse" is the diverging, or "curved", one. Railroads avoid as much as possible having the normal route curved and the reverse either more curved or, as in the case you describe, "straight", but when reasons of space and geography dictate, they do install them.

Examples of what you describe are: the switch in the main line for the east leg of the wye on the Santa Fe at Calwa in Fresno, CA; switch in the siding for the west leg of the wye at Jastro just west of Bakersfield, CA, also on the Santa Fe. For both of these the "main line" speed was 40 and the turnout speed was 10. The old power switch at Martinez on the SP was like this, normal for the Cal-P (curved) and reverse for the Mococo line to Tracy ("straignt")--the speeds were 30 and 25 respectively. All three of these have been removed.

The north (formerly "east") switch of Penoyar, CA, on the SP's Natron Cutoff (between Dunsmuir, CA and Klamath Falls, OR) is a good example of normal being curved and reverse being even more curved: 70 mph MT on a RH curve with 25 mph RH turnout into the siding, which is still in service.