Traffic in Houston's EZ Tag lanes was down 7 percent on Tuesday after the 25 cent toll increase went into effect compared to the week before.
Officials attributed the dip in part to some commuters stretching out their Labor Day weekend, but some may have decided to take other routes because of the higher toll.
"It could be either, or both," said Patti Evans, spokeswoman for the Harris County Toll Road Authority. "The best way to get a feel for whether the toll increase has affected traffic is to see its effect over a longer period of time.
"If the numbers are still down next week, we'll know it's not the holiday."
Evans was emphatic that the modest toll increase "wasn't intended as congestion pricing" -- setting tolls high enough to persuade some drivers to take other routes or commute at other hours.
Overall traffic counts were not available, but the electronic EZ Tag monitors showed 272,126 motorists systemwide from 6 a.m. to 10 a.m., compared with 291,996 for the same hours on Tuesday, Aug. 28, a decline of 6.8 percent.
For the crowded Westpark Tollway, which accepts only EZ Tags, the count fell 5.3 percent.