California Unified Cycle (UC)

The California Unified Cycle (UC) is a dynamometer driving schedule for light-duty vehicles developed by the California Air Resources Board. The test has been also referred to as the Unified Cycle Driving Schedule (UCDS) or as the LA92 (also spelled LA-92) cycle. The test is often called the “Unified LA92”, to distinguish it from a “short LA92”, which includes the first 969 seconds of the Unified LA92.

The UC cycle is used as one of the Supplemental Federal Test Procedure (SFTP) emission tests for Tier 3/LEV III and later MDV vehicles with GVWR of 10,001-14,000 lbs. Another application of the UC cycle is testing of vehicles fitted with direct ozone reduction technologies (the SFTP procedure was used for that purpose earlier).

The UC test, Figure 1, has a similar three-phase structure, but is a more aggressive driving cycle than the federal FTP-75; it has higher speed, higher acceleration, fewer stops per mile, and less idle time. The UC test is run in the following manner: Phase 1 and Phase 2 are run consecutively, followed by a ten minute hot soak, then Phase 3 which is a duplicate of Phase 1. Emissions from each phase are collected in a separate sampling bag. Overall cycle emissions are calculated in the same manner as the weighted, overall FTP-75 formula, taking actual mileage from the UC into account. In some applications, Phase 3 of the cycle is skipped and only Phase 1 and 2 are run.

The following are some characteristic parameters of the cycle:

• Unified Cycle—Phase 1 + 2 + 3:
  • Duration: 1735 s
  • Total distance: 11.04 miles (17.70 km)
  • Average Speed: 22.92 mi/h (36.74 km/h)
• Unified Cycle—Phase 1 + 2:
  • Duration: 1435 seconds
  • Total distance: 9.8 miles (15.8 km)
  • Average Speed: 24.8 mi/h (39.6 km/h)
• Phase 1 (Bag 1):
  • Duration: 300 seconds
  • Total distance: 1.2 miles (1.9 km)
• Phase 2 (Bag 2):
  • Duration: 1135 seconds
  • Total distance: 8.6 miles (13.8 km)