The Traffic Comparison Numbers

PictureClick to view the Traffic Comparison PDF
Here we compare the traffic numbers for a potential subdivision, the questionable Isakson Living traffic study numbers, and some more realistic estimates of the real traffic impact of an Isakson Living CCRC.  Traffic engineers figure the amount of traffic a development would generate by using the Institute of Transportation Engineers (ITE) Trip Generation Manual, 9th Edition, and we include a chart explaining all the numbers used in calculating the traffic impact.  Isakson Living used the absolute lowest category possible from the ITE manual, and this chart explains why other ITE categories would provide a more precise traffic prediction for this development.

It must be pointed out that Isakson Living's traffic study didn't use the ITE manual's "Continuing Care Retirement Community" or "senior housing attached" traffic numbers.  Rather, they used traffic numbers for "congregate care facility", and "units" rather than "occupied units", which of course use lower multipliers.  Still, even using their "congregate care facility" traffic numbers, the Isakson Living development would create more than twice the traffic of a reasonably sized subdivision would. 

Because of the unusually low number of assisted living units and nursing care units (11% combined) and the high number of independent care units (89%) in the latest Isakson Living CCRC proposal, it seems apparent that the proposed CCRC should be calculated as a "senior housing attached" (also known as senior apartments) development, and those ITE traffic numbers should be used.  Note that in using the "senior housing attached" Isakson Living's traffic impact of their first proposal would generate 3,289 car trips a day.  Why is 3,289 important?  Isakson Living was required to get a Development of Regional Impact (DRI) clearance from the state of Georgia, because the development's impact "is likely to have regional effects beyond the local government jurisdiction in which they are located." In particular, a DRI review was required because the proposal had more than 400 units in an established neighborhood (in fact, both proposals have had more than twice that number of units).  However, Isakson Living got an expedited DRI review because their traffic study showed fewer than 3,000 daily trips (DRI reviews for proposal with more than 3,000 daily trips take longer and are more thorough). The state of Georgia could have had the opportunity to conduct a more thorough review of the Isakson Living plans, had Isakson Living used the "senior housing attached" ITE traffic numbers.

We also wonder why Isakson Living didn't have an independent analysis of a real CCRC community for a more realistic traffic estimate.  Other potential CCRC developers often commission a study of an existing CCRC's traffic to anticipate and plan for a new CCRC's actual traffic impact, and these studies often find traffic is even higher than the ITE traffic numbers.  One example of this is used in the comparison chart. 

Note that the traffic impact for the 'alternative use traffic study' that Isakson Living asserted on page 34 of their first zoning proposal are all highly improbable if not impossible, and  the ITE multipliers used in the traffic analysis are incorrect.  At any rate, any commercial endeavor for the Tritt property would be contested and the zoning rules would be on the side of the surrounding residential neighborhoods based on the Cobb County future land use plan.