left-turn lanes, and turnarounds, and easy access to US 75 and I-635 Level III: I-635, ten regular lanes, five going each way, and four HOV lanes (two going each way) separated by barriers Levels IV and V: Direct connection ramps (two levels), eliminating the left exits of the modified cloverleaf The interchange, with its decorative etchings on precast concrete elements, along with the visually appealing coloration specified by the Texas Department of Transportation (TxDOT), can be regarded as an enormous work of public art. The High Five also incorporates a hiking and bike trail, named the Cottonwood Trail, which runs under all levels of the interchange. The section of the trail passing beneath the interchange was constructed as part of the High Five project by TxDOT. History The High Five Interchange project was planned as a replacement for the existing antiquated interchange, which accommodated 500,000 vehicles daily and was located in one of the most intensely developed commercial zones in Dallas. It was a collaborative project between the TxDOT, affected motorists and property owners, and the primary contractor, Zachry Construction. An essential consideration was to complete the project with as little disruption to the traffic flow as possible. Reasons for upgrading the interchange, in addition to the need to increase traffic flow and reduce congestion, were to improve air quality, safety, and local access. Zachry Construction Corporation submitted the lowest bid and was awarded the $261 million contract by TxDOT, the largest ever by that agency. The construction contract for the High Five Interchange was unique in that it contained elements not found in other construction project contracts. For example, it specified the concrete maturity method to be used to ensure the concrete's strength (the first time TxDOT had ever done so), and contained an early-completion bonus, a sliding scale of up to $11 million if the company completed the contract within four years. Also built into the construction contract was a provision that Zachry be charged for "lane rentals" by TxDOT for time they closed down traffic lanes—fees based on hourly assessments and the time of day the lane was closed. The fees ranged from $50 to a high of $110,000 for rush hours. In order not to interfere with traffic flow during construction, the new interchange was designed largely as elevated flyover ramps and viaducts so they could be built high over the existing junction lanes; once traffic