  At the High Luminosity LHC (HL-LHC), the CMS experiment will face a harsh
environment with a high instantaneous luminosity up to 7x10$^{34}$/cm$^2$/s
corresponding to an average of 140-200 multiple proton-proton collisions per
bunch crossing. The main goal of the CMS Level 1 (L1) trigger upgrade for the
HL-LHC is to maintain trigger thresholds that are as low as possible and
comparable to those currently in use at the LHC, and to possibly include new
triggers that were not feasible at the LHC. This will be achieved by upgrading
the detector readout electronics, to allow a much larger L1 trigger rate, and
by including, for the first time, tracking information in the L1 trigger.
Examples of how this tracking information can be used to reduce the L1 trigger
rates are presented.
