According to Ami Cholia at Alttransport, the peak charges implemented on the Bay Bridge at San Francisco from July 2010 are working. This was reported previously in the context of San Francisco seriously considering a downtown cordon based congestion charge.
The Bay Bridge toll (full schedule here) is usually US$4, but from 0500-1000 and 1500-1900 weekdays it has been increased to US$6. Interestingly it is US$5 all weekend, implying that weekend volumes are a bigger issue than the inter-peak. High occupancy vehicles (defined as 3+) are eligible for a discount rate of US$2.50 only if they have a “Fastrak” DSRC tag account. Previously HOVs had free access (vehicles with three or more axles pay significantly more).
Apparently, this single move has reduced travel time by 4 minutes westbound (citybound) in the AM peak. It was also reported that patronage on the BART rapid rail transit line that parallels the bridge route increased by 4,000 at that time. Interestingly, HOV vehicle usage dropped by 29%, which indicates time shift and mode shift in travel by groups in cars.
Introducing variable peak charges on already tolled bridges is proving to be increasingly popular. One can only hope that this relatively simple step (which could be paralleled with lower charges during low periods of use if there were concerns about revenue maximisation) can be observed more widely and more seriously considered elsewhere.