excessive volume of traffic on Deerfoot Trail is a contributing factor to the 10,000 collisions recorded between 2002 and 2007, including 24 fatalities. Constable Jeff Klatt of the Calgary Police Service stated that there is a "consensus among police officers that it’s dangerous to do traffic stops" on Deerfoot Trail. A 1993 incident in which a stolen vehicle struck and killed a police officer on Deerfoot was the catalyst for the Calgary Police Service's acquisition of a helicopter. 2013 statistics confirmed that Deerfoot Trail had more crashes and traffic jams than any other road in Calgary. Deerfoot has many entrances and exits in close proximity which exacerbates problems, but some have attributed a portion of the congestion to driver error. Constable Jim Lebedeff of the Calgary Police Service stated, "a lot of people don’t understand, or don’t want to understand, how to merge properly." 30% of respondents to a 2016 poll stated that the main reason they avoid Deerfoot Trail is because they do not feel safe on the freeway. In 2015, plans for improvements to Deerfoot Trail near Southland Drive were cancelled and a study was initiated to determine the best course of action to begin improving the freeway. The Calf Robe Bridge is also prone to collisions as its concrete deck becomes slick in cold weather, and large curves precede and follow the bridge. A 1996 crash on the bridge claimed the life of a teenager when her northbound car struck the rear of a fire truck parked in the left shoulder attending to an accident in the southbound lanes. Poor visibility due to the curve prior to the bridge was a contributing factor in a successful lawsuit by the girl's family against Calgary. Interchanges The freeway features 21 interchanges of varying design. The most recent interchanges to be constructed at the north and south ends of the freeway are more consistently of the partial cloverleaf type, a design highly used in Alberta as it is a desirable compromise between cost and capacity. The two interchanges with Stoney Trail are cloverstack interchanges, where high capacity directional flyovers carry traffic turning left for movements with more traffic, and loop ramps service lesser used left turn movements. Older and less efficient designs are used at Deerfoot's intersections with both Glenmore Trail and Highway 1. The junction with Glenmore is an incomplete cloverleaf interchange; traffic northbound on Deerfoot does not have