Cloverleaf Interchanges Outdated

"So ubiquitous is the cloverleaf design with its four circular ramps -- resembling a four-leaf clover -- that cultural critic Lewis Mumford once joked that it had become the national flower... A 1999 study by the Virginia Department of Transportation concluded that cloverleaf interchanges begin to bog down when traffic surpasses 1,000 vehicles per hour. During peak rush hours, the cloverleaf intersection of the Riverside (91) Freeway and the Pomona (60) Freeway — now being rebuilt at a cost of $317 million for four years of construction — carries about 14,600 vehicles per hour in each direction."

Thanks to g edward freeman