The Bronx River Parkway’s success inspired planners from around the world. In creating the nation’s first public automobile parkway, the BPC commissioners, engineers, and landscape architects introduced a set of parkway principles that evolved to became standard features for future parkways and modern freeways. These design principles were not invented by the BPC, but the Bronx River Parkway is generally acknowledged to be the first large-scale public motorway where such features were employed in a comprehensive and systematic manner. The design principles included: curvilinear roadways that followed the natural contours of the landscape, grade separations, medians, separated roadways on varying grades, a broad right-of-way, limited access, and a naturalistic landscape. While the BPC did not include all its parkway principles in all areas of the drive, the WCPC used them with increasing regularity on later parkways and they eventually became standard components of modern freeway construction. Another major Bronx River Parkway-related innovation that had a profound impact on subsequent parkway and highway development was Arthur Hayden’s design for the rigid-frame bridge. More than ninety rigid-frame bridges were built in Westchester County between 1922 and 1933. Approximately 400 were built elsewhere in the United States prior to 1939. Rigid-frame construction was soon adopted by highway builders throughout the developed world.(308)

During the second half of the twentieth century, the parkway was widened and straightened in many areas and steel guardrails and other modern safety elements were added. These modifications improved the parkway’s safety and efficiency, but in many places they have seriously compromised the Bronx River Parkway’s scenic beauty and historic integrity. The loss of historic integrity is particularly evident south of Sprain Brook Parkway where the originally four-lane roadway has been expanded to six lanes and straightened significantly. Although the six-lane roadway resembles a conventional freeway in many respects, it retains some of the original rock retaining walls, landscaping, and several bridges. Most of the Westchester County portion of the BRPR continued to serve its original function as a multi-purpose recreational area, transportation corridor, and environmental protection reservation. Despite a number of alterations to the original design, the Bronx River Parkway north of the Sprain Brook Parkway was placed on the National Register of Historic Places in 1990.

When the Historic American Engineering Record documented the Bronx River Parkway in 2001, ongoing modifications continued to impact the parkway landscape in ways that threatened to compromise the integrity of the original parkway design, even in the designated historic section. These developments included natural processes such as volunteer plant growth and siltation, which impinged on designed open areas and degraded various water features, and deliberate interventions endorsed by parkway managers, including pavement widening intended to increase safety and efficiency and the authorized planting of trees, shrubs, and flowers in areas designated as open meadows in the original parkway development plans. The research and documentation provided by the Historic American Engineering Record is intended to enhance scholarly understanding of America’s engineering accomplishments and offer resource managers baseline information about the historical origins, cultural significance and current conditions of sites of great importance to America’s engineering heritage. The Bronx River Parkway Reservation is clearly such a site. As the first public parkway explicitly designed for automobile use, a widely acknowledged prototype for the modern, high-speed motorway, and a model for regional recreational planning and environmental rehabilitation, the Bronx River Parkway Reservation is clearly one of the most significant developments in the annals of twentieth century American civil engineering, regional planning, and landscape design. Its importance to the citizens of New York City and Westchester County is equally significant. Seventy-five years after its official completion and nearly a century after its original conception, the parkway continues to fulfill its intended function as a scenic reservation, recreational resource, and transportation artery that combines beauty and utility, nature and culture, preservation and innovation.

(308)Hayden, "The Rigid-Frame Bridge," 184.