[sudev]

Excellent suggestions.

* Be extra careful of driving during rain.

* Heavy rain means puddles and heightened chances of aquaplaning.

* Intermittent rain after a long day spell means muddy road surface. This will be even more slippery. True also for city roads.

* Rain also means reduced vision clarity making it even more difficult to watch peripheral vision objects like children or animals dashing across.

* Rain also means momentary madness by pedestrians intent on keeping dry / out of shower. Watch out just when it starts to rain.

* Rain means even poorer night vision compounded by glare from water on windshield.

* Rain can hide dangerous potholes and cave in's.

[ssambyal1980]

It's always advised to drive in a lower gear whenever going downhill so as to make maximum use of engine braking. Engine braking occurs when the retarding forces within an engine are used to slow down a vehicle, as opposed to using additional external braking mechanisms. One can shift into 3rd or 2nd or 1st gear, depending upon the level of descent.

Engine braking is less in petrol engine as compared to diesel engine due to the very fact that the stroke is less in a petrol engine than in a diesel engine. The stroke is the maximum distance which the piston travels within a cylinder between the TDC and the BDC

TDC or Top Dead Center is the top most point in a cylinder, to which the piston moves during the compression stroke.

BDC or Bottom Dead Center is the bottom most point in a cylinder, to which the piston moves during the exhaust stroke.

In a diesel engine cylinder, the piston travels more in between the TDC (Top Dead Center) and the BDC (Bottom Dead Center) thus resulting in more exposure to frictional forces, hence more retarding force is generated. Whereas in a Petrol engine cylinder, the distance travelled by piston is less.

During my numerous trips to the hills in Himachal Pradesh, I have always made it a point to shift to a lower gear whenever coming downhill, so that the pressure is off the brakes to some extent, nonetheless its imperative to use the brakes in between but in a pumping fashion, thereby preventing them from getting too hot, which might eventually lead to a total braking loss.

In between use of braking will also ensure that the engine is not overrun. Overrunning of engine occurs when vehicle is being driven downhill in lower gears with foot off the accelerator pedal. In this situation, with increase in vehicle speed, the rpm of the wheels also increases, which gets transferred back to the crankshaft through gears, eventually increasing the rectilinear motion of the pistons, resulting in engine overheating.

In one of my trip to Jalori Pass (Altitude 3,120 meters AMSL) in Himachal Pradesh in a Maruti 800, I came across a very useful advisory by the HPPWD regarding the use of engine braking.

Jalori Pass is although not a very high altitude pass, as compared to other high motorable Himalayan passes but still its ascent is a very steep drive (considering that the altitude increases by over 2,300 feet within a distance of 6kms between the village of Khanag (Alt 2,420 meters) and Jalori Pass (Alt 3,120 meters), which then decreases by 1,700 feet between Jalori Pass and Shoja (Alt 2,600 meters) within a distance of 5kms on the other side). This results in an equally steep descent when coming downhill from any side. Both the situations are quite demanding on the vehicle with a drive in 1st gear only, especially during the downhill drive.

Here's the snapshots of that advisory:

[honeybee]

I think it is pretty normal to use the brakes while descending steep descents. I have found that engine braking is not entirely sufficient to prevent speeding of a vehicle on decent to steep inclines, and I have used the brakes liberally with the car in second (occasionally third gear where I felt the speed was too much for the second to handle and the road was straight).

Let the brakes rest by taking your foot off them once in a few moments, don't keep riding them all the while. As long as you start at a slow speed and keep tapping the brakes gently and don't accelerate you should be safe.

[honeybee]

Cannot stress this enough, but please follow the speed limits. They are there for a reason. If you follow them, you will find that you can make emergency stops much better without compromising your own vehicle or any other vehicle. Just because someone else doesn't seem to worry about a 20kmph warning posted on a village road with a school nearby doesn't mean you should ignore it too.

Driving at sedate speeds often keeps you fresh for a longer duration. From my personal experience, when I have been driving at triple digits speeds, I have always been at the edge of my seat (figuratively), and tense and always scanning my surroundings without any time to have small talk or enjoy music. Sometimes I have been irritated by the small talk made by the car's occupants when I felt like shouting, "Hello! I am trying to drive here!". But the moment I drop to 80kmph or thereabouts, I feel more relaxed and the stress is gone. No point in reaching early by a few minutes with everyone hating you for the scotch tape on their mouths!

And on long journeys, take frequent breaks - every hour, or at least once in two hours. Get out of the car, take a small walk, have tea and snacks, or just relax. It helps relieve some stress and prepares you for the next stretch with a better mindset.

[sanjaykk]

Might be a noob observation or totally wrong, but let me put it here for expert comments:
I have noticed that when the clutch is depressed to shift gear (in this case shift to a lower gear) the vehicle picks up speed. Especially in ghat sections when one has to alternate between gears (mostly second and first) this is very noticeable.

[shankar.balan]

Always use engine braking as much as possible. Always control speed by tapping the brakes lightly as required.
When descending a steep incline, please always use the same gear as you would have needed to, while ascending the same incline.
Never ride your brakes, you will cause them to overheat and then fail and then, bye bye.
Petrol engines will not have the same engine braking capacity as Diesels do, so you should never upshift while descending a very steep incline. Even if the car feels like it is grinding along in 1st gear down the incline, for safety's sake, until you reach relatively level ground, please continue only in first gear. While descending steep inclines please always stop on a regular basis to give the vehicle and yourself a short rest. Use these rest stops for photography.

[ssambyal1980]

Wear seat belts at all times, even if the vehicle has to be driven slowly over a short distance. Studies have shown that a front end collision even at a humble speed of 15-20 km/h, can land up one with a broken nose, if driving without seat belt.

This is because the intensity of collision is in direct proportion to the relative speed of the vehicles involved in collision. Relative speed of two vehicles moving in opposite directions is the sum total of the speeds of both the vehicles.

No matter if speed of one vehicle is say a mere 20 km/h, and the same is the speed of the other vehicle, then relative speed comes out to be 20+20=40 km/h, which is pretty high to cause serious injuries.

So it feels pretty scary to even think of the outcome of head on collisions between two vehicles moving at high speeds, with passengers without seat belts.

Seat belts also save lives in case the vehicle topples over. With seat belts on, passengers will remain glued to the seats, thus preventing any serious injury.

Wearing seat belts is the most easiest and quickest way to ensure safety while driving.

[sudev]

First of all hill decent control is also using brakes and engine. Only it is done in preprogrammed system.
When the incline is very steep the engine is also overcome due to forces acting upon it. In such case continuous braking is the solution along with rests to ensure cooling off brakes and discs / drums. Though all normal roads are built and designed not to stress brakes soo much. Small steep stretches are not a problem on combination of engine plus first great plus brakes.

@sanjaykk when clutch is pressed on downhill stretch gravity accelerates vehicle to go faster. That is why use of engine braking by keeping car in gear with no accelerator.

[ssambyal1980]

@sanjaykk

Originally Posted by sanjaykk

I have noticed that when the clutch is depressed to shift gear (in this case shift to a lower gear) the vehicle picks up speed. Especially in ghat sections when one has to alternate between gears (mostly second and first) this is very noticeable.

You have made a good observation. This is experienced by one and all when going downhill. Actually what happens is, that when vehicle is moving in lower gear, with foot off the throttle, the engine braking comes into play, which provides retardation and hence keeps the speed under control.

The moment one presses the clutch to change over, the drive to the wheels gets disengaged and wheels become free. So with no engine braking acting on them, the vehicle tends to move faster.

[Aroy]

Originally Posted by rohanak1

Hi guys,

I own a Renault Duster RxL petrol model which I purchased in 2014. On a trip to Coonoor I was returning from the "Acres Wild farmstay". The roads here are broken and extremely steep. While returning downhill, I was finding it tough to control the car speed even in the first gear. The car sped off and was touching 4500rpm. I needed to use the brakes repeatedly to reduce the speed and rpm's. Using brakes repeatedly downhill is not a good idea I believe. Is there any way of controlling speed in such situations provided many cars do not have hill descent control?

If you start at higher speeds, then on steep descents it may not be possible for the engine to reduce the speed, so as suggested, start the descent at slow speed in first gear, and then use the brakes judiciously.

[ssambyal1980]

Apart from wise and judicious use of brakes along with engine braking to slow down the vehicle, specially fitted speed retarders also help in controlling the vehicle speeds when going downhill. These are mostly used in heavy vehicles. Have read that most of the Volvo buses being driven in India have them as a standard fitment.

[sidharth_j]

Well, having done a fair bit of highway drives in the last year, here are my observations -

1) Always stick to speeds between 80-95km/hr. These are reasonably good speeds to maintain over long periods, you don't get tired that easy, and you most often have enough reaction time to cover for surprises.

2) If on a four lane highway, stick to the left lane for the regular driving and use the rightmost lane ONLY for overtakes.

3) Take regular breaks - at least once in 2 hours. Stop preferably at well known food joints. Meaning prior to your journey, plan out where you would be stopping

4) Always have more than at least 1/3rd of your tank filled with petrol/diesel, you dont want to run out of gas at the wrong time

5) Keep your vehicle's 24/7 service line number ready. along with the NHAI helpline.

6) Keep your tyre pressures as close to manufacturer recommended limits for your long drives.

7) Keep your windscreen clean.

8) If ever you have to drive through heavy rain/cloudbursts, reduce your speeds and switch on the emergency lights and the headlamps on low so as to increase visibility. I was caught in one such outside Dharmapuri last weekend and visibility dropped to zero pretty fast.

9) Never overtake on blind turns - goes without saying.

I also make it a point to always plan out the route and alternatives in case of diversions. It is useful to carry an offline gps with you for navigation as well.

Regards,
Sid

[dhanushs]

Originally Posted by ssambyal1980

Engine braking is less in petrol engine as compared to diesel engine due to the very fact that the stroke is less in a petrol engine than in a diesel engine. The stroke is the maximum distance which the piston travels within a cylinder between the TDC and the BDC

TDC or Top Dead Center is the top most point in a cylinder, to which the piston moves during the compression stroke.

BDC or Bottom Dead Center is the bottom most point in a cylinder, to which the piston moves during the exhaust stroke.

In a diesel engine cylinder, the piston travels more in between the TDC (Top Dead Center) and the BDC (Bottom Dead Center) thus resulting in more exposure to frictional forces, hence more retarding force is generated. Whereas in a Petrol engine cylinder, the distance travelled by piston is less.

Hi, there are long stroke petrol engines, as well as short stroke diesel engines. What will be the engine braking in such cases, if like you mentioned stroke length decides engine braking?

[ssambyal1980]

Originally Posted by dhanushs

Hi, there are long stroke petrol engines, as well as short stroke diesel engines. What will be the engine braking in such cases, if like you mentioned stroke length decides engine braking?

Hi, absolutely agree with you. Just tried to explain from a layman's point of view, as normally diesel engines call in for a longer stroke to enable higher compression ratio.

Would like to share that personally I've never delved that much deeper into the technicalities of internal combustion engines but nonetheless engine braking behaviour of long stroke petrol engines and short stroke diesel engines, definitely calls in for an insight.

Regards

[ssambyal1980]

* Lane driving is the yet another important factor contributing towards safe driving. The extreme far right lane on any four, six or eight lane highway, is meant for overtaking purpose only, hence one should immediately move to the left lane after overtaking the vehicle.

* Always keep a good amount of distance between your vehicle and the vehicle in front of you, so as to avoid tail end collisions in case of sudden braking.

* Always drive at speeds which allows you to gel well with the prevailing traffic conditions, as unnecessary acceleration and braking would not only result in lower fuel efficiency but will also result in fatigue build up.

* Avoid overtaking vehicles unnecessarily just for the sake of it. Always make it a habit to drive at uniform speeds, as this will add up to the fuel efficiency of the vehicle.