Scene of an early morning accident between a school bus and a dump truck Thursday, October 18, 2007, in Calgary, Alberta. (Chris Bolin/Canadian Press)

Twice a day, as often as five days a week, about three million children hop onto bright yellow buses to head towards, and return from, school. Most of the time it's an uneventful part of a child's daily routine, but occasionally, the trip takes a tragic turn.

On Oct. 18, 2007, a school bus crashed on a busy freeway in Calgary during morning rush hour, claiming the life of one girl and injuring several others. And on April 11, 2007, 10-year-old John Pham died when the school bus he was riding, en-route to a field trip, collided with a tractor-trailer in Brampton, Ont., west of Toronto.

With each tragic incident, safety advocates raise the addition of seatbelts to school buses as a possible solution. But even the experts aren't completely certain whether the measure would make school buses safer.

How many passengers?

• Three million children ride school buses a day.

What are the common causes of injuries related to school buses?

• Seventeen per cent of injuries occur when people enter or exit the bus, according to a sampling of school bus injuries by the Canadian Hospitals Injury Reporting and Prevention Program (CHIRPP).
• Fifteen per cent of injuries happen when the bus is involved in a motor vehicle accident.
• Twelve per cent happen in violence within the school bus between passengers.

Who gets hurt?

• According to the CHIRPP report, most of the injuries in school buses happen to children from kindergarten to Grade 9.
• Fifty per cent of injuries happen to children aged 10 to 14 years of age.
• Thirty-seven per cent are aged between five and nine.

When?

• According to the CHIRPP report, 13 per cent of injuries take place in summer months.
• Thirty-seven per cent in the fall months.
• Forty-nine per cent of injuries happen between noon and 4 p.m.
• Twenty per cent of injuries happen in the morning hours.

How often do school buses crash?

• Between 1992 and 2001, 26,039 school buses were involved in 25,806 collisions, according to a Transport Canada report.
• Of those crashes, 129 were fatal collisions, 4,971 involved personal injuries and 20,706 inflicted property damage.
• Collisions in which someone either died or was injured that involved at least one school bus make up about 0.3 per cent of the 1,609,927 casualty-producing collisions involving all vehicle types, according to Transport Canada.

Deaths in school bus accidents

• 145 people have died in vehicle collisions involving school buses between 1992 and 2001 — about 14.5 a year, according to Transport Canada.
• Of those 145 total fatalities, six were school bus occupants (less than 19 years old)
• An average of one (0.6) school bus occupants died per year. Three of these six fatalities occurred in 1994, one in 1999, and two in 2000.
• One bus driver died in a school bus collision during the same time period, in 1998

Injuries in school bus accidents

• School bus collisions have resulted in 9,359 injuries between 1992 and 2001, an average of 936 injuries per year, according to Transport Canada.
• Of those injured, 3,369 were school bus occupants — an average of 336.9 a year.

Seatbelts

Transport Canada says "there are few instances where seatbelts would prevent injury in school buses." It notes that seatbelts are not effective in many cases, such as when an object breaches the vehicle's plating. However, it notes that seatbelts could prevent injuries in rollovers, ejection from the bus and impact with other vehicles. Modern school buses have a "passive restraint system," or "compartmentalization," that does not involve seatbelts. Passengers are protected by high-backed seats that are heavily padded and spaced close together. This type of system absorbs impacts in the event of a collision or a rollover.

Belts are in use in some jurisdictions, for example in Etobicoke, Ont., New York and New Jersey. A study in the late 1980s said $8,000 would be the cost to install seatbelts in a 50-seat bus.

Transport Canada does not call for seatbelts in school buses, but for small children who weigh less than 18 kilograms, it has made it mandatory that seats be fitted with tethers to attach child seats for pre-school children. This came into effect in April 2007.

There are other ideas, but not in wide use. For example, two researchers at Johns Hopkins University thought that mimicking the safety bar on roller coasters would transfer on school buses. In 1999, Stephen Pantano and William Thompson created a restraining bar system like those used in the amusement park rides. They proposed that the bar would be bolted to the floor, and once children were seated, it could be locked into place.