Yellow line
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How and why Yellow Line Laws are used and abused

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You are entitled to cross that central line (whether it is solid or broken) only if it is “safe” and “necessary”. 

Photo credit: Shutterstock

Question: Is it true that crossing a solid yellow line is always and automatically an offence, no matter what the circumstances? 

Answer: No.  There are many instances where crossing a continuous (solid) yellow line is permissible. So many that the law cannot rationally list them. So the law defines the position the other way around: Crossing a solid yellow line is not an offence unless it is done carelessly, recklessly or dangerously. 

First and foremost, both continuous and broken yellow lines define the boundary between lanes of traffic travelling in opposite directions. The law says you should generally stay in your lane, normally positioning your vehicle in the middle of it; neither too near the edge nor too near the centre.

You are entitled to cross that central line (whether it is solid or broken) only if it is “safe” and “necessary” to do so - eg for overtaking or going around an obstruction. Not, say, for cutting corners.  

Before making a manoeuvre which crosses a yellow line, you should check your rearview mirror, indicate your intention, and double-check that the road ahead is clear of oncoming traffic. That means you must be able to see – without a doubt - that any oncoming traffic is far enough away for you to complete your overtake and return to your own side of the road without causing any other vehicle (neither the vehicle you are overtaking nor oncoming traffic) to alter its speed or line. You must also be able to see, in advance, that there is ample space for you to return to your side without delay or disruption. Broken yellow lines serve this primary purpose adequately where the road is relatively flat and straight. 

Solid yellow lines have a secondary purpose where the road has potentially “blind” brows or corners or passes between bridge railings (where there is less room – eg no verge for evasive action). So on the approaches to blind bends and brows, the broken line becomes solid to warn you that - in normal circumstances – your view ahead is too short to safely attempt an overtake.

The distance before a blind bend or brow where the solid line begins is guided by international standards, which allow for the likely variations in the speed of ambient traffic in a particular location. 

Whatever the speeds, a conventional overtake requires the faster vehicle to “gain” about 100 metres over the slower one during the manoeuvre. The time and distance required to do that depends entirely on the actual speeds of the two vehicles. 

To save you the maths, a vehicle travelling at 100 kph is covering ground at 30 metres per second. If it is overtaking a vehicle moving at 70 kph (20 metres per second) it will “gain” ground at 10m per second. So it will take 10 seconds to “gain” 100 metres. In those 10 seconds, the faster car will cover 300 metres. 

If it is overtaking a slow truck doing only 20kph (about 5 metres per second), the faster car will gain ground at 25 metres per second and take only four seconds to complete the overtake. In that time, the faster car will travel only 120metres.  

The safety margin also depends on the speed of oncoming traffic which might appear over the brow or round the corner while the overtaking manoeuvre is in progress. The oncoming vehicle might be a car approaching at 30 metres per second or a truck approaching at 5 metres per second – a sixfold difference! 

The length of the solid yellow line cannot be a one-size-fits-all.

Just as clearly, it needs to be long enough to cover a worst-case scenario. And that means much too long for efficient flows when some traffic is very slow.

You might think that it is not too much to ask a faster car not to overtake for 300 metres or more when it comes up behind a very slow vehicle at the start of a solid yellow line. The car should just stay behind a crawler for 300 metres (even when nothing is coming the other way). 

Once or twice, maybe. But on a trip from Nairobi to Mombasa, this situation will not happen once or twice. It will happen 100 or 200 times.

Even in countries with advanced systems, where virtually all vehicles are travelling at relatively similar and quite high speeds, excessive stop-start disruption of flow is not acceptable. And there is a simple solution:

CROSSING A SOLID YELLOW LINE IS NOT AN OFFENCE in itself. If it is necessary and can be and is conducted safely, it is allowed. Why wouldn’t it be? Only if overtaking is done recklessly or dangerously (whether at a solid or broken line) can it be prosecuted.

That caveat does not seem to have found its way into the traffic police training manual in Kenya. It is currently the favourite pastime of roadside checks on trunk roads to conceal themselves around a corner or over a brow and charge motorists (even if they have overtaken a very slow truck perfectly safely) with “overtaking at a solid yellow line”. Without evidence of the “careless/reckless/dangerous” element, such charges should be thrown out of court. But, of course, such cases rarely if ever get to court anyway. 

The situation is made worse by our proclivity for illegible or incorrectly positioned solid lines (in some cases where there is a clear view for 2 km or more ahead), and an acute shortage of instances where the lines are solid on one side (approaching a brow or corner) and broken on the other side (after cresting a brow or completing a corner). 

There are, of course, technical remedies for these challenges, such as a third style of line in the discretionary transition between broken and solid lines (eg doubling or trebling the length of dashes in a broken line). Such systems are widely used in other countries. 

Right now, our road marking system is defective. Enforcement is defective. And compliant motorists carry the can for both those faults. I believe competent and diligent motorists are stopped hundreds (even thousands )of times per day, countrywide, on the solid line issue. To the best of my knowledge no designer, contractor or inspector has ever been charged with painting lines in the wrong place…or not at all.

The anomalies are not few. There are thousands. But instead of reporting the anomalies, the police welcome them. They are a “business” opportunity, perhaps backed up by a last-resort ethos to curb delinquent behaviour through threat and fear of punishment, because a limited enforcement resource and lack of public education and respect have not worked.

That scenario should never justify the level of autocracy currently granted to enforcement, but it might help explain it.