Bridges & Structures Division senior engineer Chan Che-keung said that the department is studying the viability of planting grass on top of footbridges, and considering expanding the scale of 'vertical greening' such as on noise barriers and under bridges.
He said that before greening a bridge, consideration must be given to its design loading, and other issues including irrigation, drainage, impact on bridge maintenance and safety. "The biggest constraint lies in the extra weight from soil and water, as the original design loading of existing bridges might not be able to cope with it. The bridge width is another constraint as we have to ensure pedestrian flow will not be affected after putting plants on it," he said. Newly-built bridges will be made wider. For example, a 4m-wide bridge will require a 25% increase in width for a 500mm extension on both sides to provide plant space.
Other initiatives aimed at benefitting users include covering footbridges and installing lifts to give better access.
