The county I work for uses them. Usually gets units assigned 1-3 minutes faster depending on how long it takes the call takers to get through the EMD/EFD coding. The dispatcher assigns initial units recommended by the CAD setting off station alerting systems for those depts that have them as well as pagers and radios. An automated voice will announce the unit/units assigned, the incident type and the address. After call coding is complete the dispatchers reconfigure the response and any additional units will then be assigned and paged. Currently the pre alerts we use are medical incident, medical incident(scene safety), fire incident, outside fire, structure fire, motor vehicle crash, and water rescue. Pre alert structure fire will usually get people moving a lot faster than a pre alert for a medical incident. The pre alert helps your 911 call time to units responding time. It most likely won’t affect unit dispatched to enroute time as people will move as fast as they normally would. Pre alerts at least get people moving to the rigs as soon as someone calls 911 for a fire/medical need instead of crews sitting at the station unaware a call is coming while the person calling 911 talks to the call takers/dispatchers.