Potential Conflicts Reduced by Traffic Circles. Chicanes and humps also appear to reduce collisions by a large margin. Vertical calming devices receive more resistance than horizontal devices from emergency response teams because of the jarring effect they have on equipment and patients. However, the measured delay per calming device is typically less than 10 seconds with horizontal devices having slightly more delay. Care is needed not to install too many devices on primary response routes and some design alterations to devices are possible to decrease the impact on emergency response equipment.
Nice landscaping adds to the cost of circles.
Raised devices can range from simple asphalt to much more elegant patterned paving. With enough money, circles, closures, and restrictors can be beautiful landscaped features. Some citys use neighborhood volunteers to maintain the landscaping though there are liability concerns. This cuts the cost but may be more or less effective. They placed tables, benches, sand boxes and parking bays in the street, turning it into an obstacle course for motor vehicles and an extension of home for residents.