Laws should go with the flow: study finds

PUBLISHED : Monday, 25 June, 2007, 12:00am
UPDATED : Monday, 25 June, 2007, 12:00am

Safety has always been the major factor behind the push for regulating signboards. But a study backs up claims that doing so would also improve air quality in densely developed places such as Mong Kok.

The study, commissioned by the Planning Department, was completed in 2005 to assess the feasibility of establishing an air-ventilation system for Hong Kong. Overseas experts were invited to evaluate airflow in Mong Kok and Tsueng Kwan O.

According to the experts, Mong Kok's geographical characteristics and dense development resulted in poor airflow.

Data from the Observatory shows the prevailing wind mainly comes from the east of Mong Kok in summer. Since only three major roads in the district have an east-west orientation, other streets often suffer from poor airflow and the canyon effect - the trapping of heat and air pollutants because of tall buildings.

According to the study, the wind speed at pedestrian level in streets with a north-south orientation can be as low as 0.5 metres per second. The ideal wind speed to disperse pollutants and for comfort is at least 1.5 metres per second.

The study found that horizontal signboards hindered airflow. It urged the government to strengthen guidelines for district-level planning. It said vertical signboards were preferred to minimise wind blockage, especially in areas where there were many signs just above the street.

'The first priority for urban air ventilation in dense, hot and humid cities like Hong Kong is to let more wind penetrate the urban district,' the report said.

A Planning Department spokeswoman said the study recommended a set of broad design guidelines that had been incorporated into the city's planning standards and guidelines for public reference.

But legislator Patrick Lau Sau-shing noted that the guidelines were not legally binding and said legislation was necessary to regulate signboards effectively.