High Five Interchange

The High Five Interchange, north of downtown in Dallas, Texas, is a massive five-level freeway interchange. It is the junction of two major highways carrying heavy rush-hour traffic, the Lyndon B. Johnson Freeway (I-635) and the Central Expressway (US 75), and is the first five-level stack interchange to be built in the city. It replaces the antiquated three-level modified cloverleaf interchange built in the 1960s, which caused a severe bottleneck by narrowing US 75 down to two lanes at the junction of the two highways. The looped ramps of the cloverleaf forced motorists to slow down drastically, backing up traffic. Left-hand exits contributed to the congestion. Further, its two frontage roads were not directly connected to each other, making local access difficult. Alluding to the celebratory gesture, the "High Five" name refers to the five flyover ramps that tower over the landscape, handling the left-turn movements. The interchange is as high as a 12-story building The lanes of US 75, which are on the bottom level, are below ground level, giving the structure a total height of from bottom to top. The new lanes for regular traffic were built on the outer vacant right-of-way, while the HOV lanes were built in the median. The original I-635 lanes that passed through the former interchange, now demolished, were relocated between the new regular and HOV lanes. s on the second; I-635 on the third; and direct connection ramps on the two top levels From bottom to top, the roads on the five levels are: • Level I: US 75, a six-lane highway, three lanes going each way • Level II: The junction of the two six-lane frontage roads, each having three through lanes in each direction, left-turn lanes, and turnarounds, and easy access to US 75 and I-635 • Level III: I-635, 10 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 is decorated with etchings on precast concrete elements, along with coloration specified by the Texas Department of Transportation (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 (equivalent to $ in ) contract by TxDOT, the largest ever by that agency. The construction contract for the interchange was unique in that it contained elements not found in other construction project contracts. Also built into the construction contract was a provision that Zachry be charged for "lane rentals" by TxDOT for time they closed down a traffic lane, with 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 (equivalent to $ to $ in ). During the construction, of earthwork was used, of concrete was mixed on site, and of retaining walls were built. Additionally, of drilled shafts and of drainage pipe were completed. In addition to the construction of 43 permanent bridges, six temporary bridges were built, resulting in of bridge deck. The project was designed by HNTB, who provided professional engineering consultation throughout the construction, which had begun in 2002 and was completed in December 2005, more than 13 months earlier than planned. ==Recognition==

In 2006, APWA named the High Five "Public Works Project of the Year" for its massive size, its innovative design, the complexity and rapidity of its construction, and the need it fulfilled for the community. TxDOT as the managing agency, Zachry Construction Corporation as the primary contractor, and HNTB as the primary consultant received the award in recognition of their cooperative alliance in completing the project. The interchange is ranked by Popular Mechanics as one of "The World's 18 Strangest Roadways", which called it a "labyrinth of lanes" and a "five-level marvel of engineering" because of its height, the number of its bridges, and other unusual design and construction features. ==See also==