Accidents: Road designs or driver behaviour?

One key factor in road safety is speed. Each road section has a specific maximum safe speed based on its nature and expected driver behaviour. Factors such as road surface (slippery or rough) and shape (straight or curved) determine the road’s nature. The expected driver’s behaviour relates to mental steadiness and the ability to make sound decisions while driving, especially in unexpected situations.

However, the maximum safe speeds set for most roads in Uganda are often lower than the speeds at which drivers typically operate their vehicles. Speed limits are established based on these maximum safe speeds, often with a safety margin. The safety margin is considered because maximum safe speeds are calculated using theoretical assumptions that may not fully capture practical aspects.

For instance, let’s consider sections of the Entebbe Expressway, which are straight and not uphill or downhill. The Uganda Road Design Manual sets the maximum safe speed as 120 km/h, but the speed limit to be enforced by the police is 100 km/h. The enforced speed limit takes practical and operational considerations into account. Why is it important to stay within the maximum speed limit? There are three critical reasons:
1. Overtaking slow-moving vehicles on straight sections,
2. Stopping in case of unexpected obstacles on straight sections, and
3. Negotiating turns or curves without veering off the road.
Most accidents occur in these situations. Moreover, middle-line(s) road markings are based on the maximum safe speed and overtaking possibilities. Therefore, overtaking where road markings prohibit it can lead to accidents.

As a practical guideline, the maximum safe speed for many national roads, such as Kampala-Masaka-Mbarara-Kabale-Katuna, is 100 km/h. This applies to straight, generally flat sections outside of town areas. Hence, you will often see a speed limit of 80 km/h enforced by the police on these roads. Driving above both the theoretical maximum safe speed and the regulatory speed limit significantly increases the risk of accidents in critical situations.

For other sections that may be in corners/curves, going uphill or downhill, in busy/town areas, etc., the theoretical maximum speeds are much lower and the enforceable speed limits are often indicated on traffic signs before the sections start. You need to be on the lookout for these speed limits as you drive along the road.

To ensure safety, it is crucial to always drive below the speed limit. The high number of accidents may be attributed to drivers ignoring posted speed limits and overtaking guidelines.

Probably there is a need to adjust existing road designs to accommodate higher speed limits to ensure safety. But this adjustment involves reducing or eliminating curves/corners, reducing steep areas, widening existing travel lanes along with constructing extra lanes. This requires allocation of huge capital investments from the national coffers which may be untenable in the short-term considering other urgent national priorities.

Therefore, the immediate practical solution for Uganda includes raising awareness among drivers and road users, along with strict enforcement of speed limits and overtaking regulations, which can contribute to reducing accidents on our roads.

Angello  Murekye 
Civil engineer, the Managing Director at SAKM Engineering Ltd, and a PhD candidate in Transportation Infrastructure Engineering at Virginia Tech in the United States