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Cambodia needs safer street designs

Motorists wait at a traffic light on a street in Phnom Penh. Photo: Tang Chhin Sothy/AFP

If a passenger plane crashed and killed 162 people every month, there would be enormous public outrage, an intensive government investigation and a push to reform safety.

Yet similar casualty figures on Cambodia’s roads only garner condolences, tired explanations and redundant promises, never real change.

The national police reported 859 traffic accidents with 486 deaths from January through March. The cost of road traffic accidents was estimated to have cost Cambodia $466.8 million in 2019 alone, equivalent to 1.7% of the country’s annual GDP earnings, according to a report by the National Road Safety Committee (NRSC) and the United Nations Development Programme.

NRSC Secretary-General Min Manavy urged road users to respect the traffic laws, noting that 866 people involved in accidents involving motorbikes were helmetless. 

Helmets and seatbelts only mitigate injuries, they do not prevent a vehicle careening down a street and causing injuries. Instead of blaming victims, Cambodia must enact a comprehensive overhaul to examine the true culprits of traffic accidents and make a radical policy shift to solve the issue.

The Ministry of Public Works and Transportation reported overspeeding accounted for 33% of the 1,619 accidents recorded nationwide in the first half of 2020. The other factors involved in the accidents included right-of-way (23%), incorrect lane use (14%), overtaking (10%) and incorrect turning (10%). 

While careless drivers accounted for 90% of all traffic accidents in 2020, the reasons drivers speed and overtake on crowded roads, intersections or sharp turns is rarely discussed. 

Asia Injury Prevention Foundation Director Kim Panga highlighted the issue of speed. In a Phnom Penh Post interview, he recommended amending speed limits in previously implemented sub-decrees, arguing that speeds in school areas should be limited to a maximum of 30 kph (18.6 mph) while the speed limit for passenger trucks should be lowered to a maximum of 50 kph (31 mph).

Traffic police throughout Cambodia have set up checkpoints and a new speed camera system in an attempt to correct the issue, but speed limit reform is a limited, top-down approach. Traffic police cannot be expected to set up checkpoints at every street corner, nor do speed cameras address the root causes of many accidents.

Better road design is the primary tool Cambodia should apply to address driver behaviour and road safety.

Road designs

Passive and proactive designs are little-known road engineering philosophies that could significantly change the conversation.

A passive design approach accounts for the worst-case scenarios: crashes and traffic congestion. Using this approach, streets are built to contain multiple oversized driving lanes and generous clear zones to meet high traffic volumes and allow space for potential crashes. 

Evidence shows this design strategy has significant flaws, especially when implemented in urban areas where high speed is undesirable.

Emphasis on wide, simplified, and unobstructed streets causes drivers to lose their inhibitions. Generous and unobstructed driving lanes distorts judgments of speed, causing drivers to subconsciously go faster.

Driving speed increases as the lanes become wider. A 2001 study in the United States found widening lanes by 1 metre (3.2 feet) increased average speeds by 15 kph (9.3 mph). The same study illustrated that within a lane of 3.25 metres (10.6 feet), which is Cambodia’s urban street standard, driving speeds averaged an alarming 55 kph (34 mph). 

As the saying goes, “speed kills.” These passive road design choices encourage higher driving speeds and ironically lead to more and deadlier accidents.

A proactive approach to road design would increase safety in the Kingdom’s urban areas.

This careful road design strategy involves street elements which guide and influence better driving behaviour by enforcing slow and cautious navigation. These measures are crucial in significantly reducing the severity of grave injury and decreasing the chance of an accident occurring in the first place. One supporting example is a 2019 study from Ghana that found “traffic calming devices reduce vehicular speeds and, thus, the incidence and severity of pedestrian injuries in built-up areas.”

Another comprehensive American study in 1997 examined risks associated with traffic speed. A vehicle travelling at 20 kph (12.4 mph) has an accident rate of only 5% and a fatality risk of 2%. Yet doubling the speed to 40 kph (24.8 mph) was shown to triple the rate of accidents to 15% and spike the fatality risk to 5%, the report stated.

As the Kingdom moves to expand and improve its road network, adapting a proactive approach would be more efficient than retroactively modifying streets.

A passively designed street with a right-of-way of 14 metres (46 feet), where effectively all space is ceded to motor vehicles. Image: Ses Aronsakda

Safe road designs

Using various techniques referred to as ‘traffic calming measures,’ Cambodian towns and cities can reduce traffic speeds. Some interventions alter the physical configurations of roadways, while others change how drivers perceive and respond to streets.

The first alteration local designers can make is reducing lane numbers and their width from the usual 3.25 metres to 3 metres (9.8 feet) or less. Reductions help decrease crossing distance and reduce stoplight cycle time without impacting overall traffic flow

The space gained from road space reduction can be better utilised as dedicated bus and protected bicycle lanes and on-street parking buffers to protect pedestrians. This is sorely needed in Cambodia, as illustrated by an accident in which a careening vehicle on Phnom Penh’s Monivong Boulevard killed a pedestrian on the sidewalk.

An active design approach with a chicane street includes trees, street furniture, pedestrian and cyclist infrastructure. The right-of-way is preserved at 14 metres (46 feet). Image: Ses Aronsakda


To further reduce motorist speed, streets should be designed with a chicane, or a lane shifting pattern, that slows drivers with shallow turns. This can be done by alternating parking or curb extensions into the desired pattern. Working on a similar principle, a pinch-point design extends sidewalks to narrow roadways, which restricts speeds and expands sidewalk space.

Planners can also utilise roadway centre islands. Combined with raised pedestrian crossings and located in the middle of city blocks, islands reduce speeding and provide safe crossings for pedestrians and cyclists.

Psychological cues also can complement physical restructuring. Trees, street furniture and narrowed building lines create visual indicators, making drivers more speed conscious, alert and aware of their surroundings.

Protected intersections

Intersections are by far the most dangerous road locations because traffic flow converges, visibility is limited and conflict points are plentiful. The danger is heightened by drivers often ignoring stop signs, leading to tragic consequences on a regular basis.

One of Cambodia’s most infamous hit-and-run incidents occurred at a Phnom Penh intersection in 2019. An underage driver barreled through a Toul Kork intersection with an SUV, killing motorcyclist Dum Rida.

Key design features ensure road safety for all users and create streets that are more focused on people. Image: Ses Aronsakda

A preferred method of improving intersections is to narrow corners using curb extensions. This sharpens the turn radius, which encourages slower turning speeds, decreases the distances pedestrians must cross and ensures good visibility for all users as they approach the intersection.

Another effective intersection safety measure is raising crosswalks to the same level as sidewalks, signalling to drivers that they are intruding on pedestrian space and should be alert. The slight ramp also serves as a speed bump to slow drivers.

Cambodian road engineers also should pay more attention to the largest group of road users: motorcyclists. Slip lanes for motorcycles, which account for four out of five vehicles, would allow riders to line up ahead of other vehicles when stopped at intersections and reduce conflict points.

Despite decades of top-down enforcement policy, traffic accidents continue to soar at alarming rates. Over the same 30-month period, traffic accidents led to 3,599 deaths compared to 3,056 attributed to Covid-19.

Given this grim reality, the Kingdom’s approach to road safety must be reconsidered. Instead of blaming drivers, authorities and city planners must recognise the dangerous environment which the incumbent road design approach has yielded.

As the current design paradigm kills and maims indiscriminately, the time has arrived to reassess our road priorities. We must stop pursuing speed and volume for motorists and instead place greater value on health and safety for everyone.

Ses Aronsakda is a junior researcher at Future Forum. Educated as an architect, he conducts research on Phnom Penh’s urban planning with interests in all aspects of cities and urban design.

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