Would You Speed Driving Downhill in This Situation?

ozb10 on 27/04/2018 - 22:15
Last edited 28/04/2018 - 10:07 by 1 other user

There is this road that I have to pass almost daily. I believe most of us would have driven pass a road like this.

Speed limit is 60kmph, one fairly wide lane in each direction on a straight line with only 1 intersection on the left while going uphill, no pedestrian walkway or space for parking on the side I'm traveling. The road goes downhill and then back uphill to about the same level as the start.
There's an intersection with traffic light and then a short flat section just before the start of the downhill, so most cars start from zero.
There is a clear view of what's ahead as you go downhill, you will be able to see any pedestrian (rarely) or traffic in front.

Situation is if I take the car to 30-40kmph on the flat section, and just let gravity does the rest, my car will still go to 70-75 at the trough without breaking. I still have to accelerate half way up to keep going at around 60. And that's what I usually do as it saves fuel going back uphill again and also on the brakes.

I noticed:
- many others do similar thing, some may break a little but still go over the speed limit
- sometimes one or two driver will break hard and bring the speed down to 60 or less, thus all the cars following will have to do the same and then everyone will have to accelerate hard again going uphill.
- some might even accelerate while going downhill

I do drive to conditions depending on the car in front and behind me, so I either speed or break hard depending on the car in front.

So my question is, how would you drive on this road between two hills with a trough in between if you are the first car going downhill? And why?

And yes, I know what is the legal thing to do in this situation. I just want to know what other ozbgainers would do.

Poll Options

  • 2
    1. I will accelerate downhill and go over 75+ near the trough
  • 25
    2. I will not break and reach up to 70-75
  • 22
    3. I will break and reach around 65-70
  • 8
    4. I will break and reach around 60-65
  • 21
    5. I will break to 60 or below
  • 7
    6. Bikies
  • 8
    7. Other
Automotive

Comments

  • Godric on 27/04/2018 - 22:16
    +3

    Bikies

  • nocure on 27/04/2018 - 22:16

    No

  • rambutann on 27/04/2018 - 22:18
    +11

    Maintain 60kph because cops froth these situations.

    • D C on 27/04/2018 - 23:34
      -2

      I could not have been speeding because my car was in neutral! Ah ha pigs, logic for the win!

      • subywagon on 28/04/2018 - 00:19
        +2

        Are you a federal officer of the law?

        • D C on 28/04/2018 - 00:26
          -1

          I'm using less fuel so I'm saving the environment! Quit hassling me, piggy!

        • D C on 28/04/2018 - 10:54

          Downvotes? Looks like I'm being hassled by the fuzz!

          You'll never catch me!

          And I'll represent myself in court too!

          There's a thought, what's the overlap between humourless trolls and the bacon-scented ones?

  • AlienC on 27/04/2018 - 22:23
    +6

    lmao ozbargain sure does have some funny ans interesting questions.. how did I get here or better question how do I get out?

  • Baebs on 27/04/2018 - 22:23

    Yes

  • sa5ha on 27/04/2018 - 22:26
    +15

    *Brake, not break.

    • Yummy on 28/04/2018 - 00:48
      +2

      OP wants to take a tea break while going downhill, then break OP's leg.

      Uh oh.

    • ozb10 on 28/04/2018 - 08:01

      +v
      Can't believe I didn't notice it the whole time, probably needed a break indeed lol

    • havebeerbelywillsumo on 28/04/2018 - 12:39

      Op wants to know if they'll give them a brake.

  • btiltman on 27/04/2018 - 22:27

    Dammit, now we have the cops baiting on Ozbargain

    • ozb10 on 28/04/2018 - 08:39

      Yes, they are now tracing the IP addresses who voted the 60+ options and red flagging the license plates on the vehicles at those addresses :P

  • bobbified on 27/04/2018 - 22:30

    I will get out and push my car downhill and go over 75+ near the trough

    • [Deactivated] on 27/04/2018 - 23:09
      +4

      You forgot the bit where you go back into your car.

  • JIMB0 on 27/04/2018 - 23:10

    This is why hybrid/electric cars were invented, to store the excess energy in the battery and use it when going up the hill.

    • ozb10 on 28/04/2018 - 08:08
      -2

      That's +1 for those cars, but the brakes would still wear out faster.

      • coxjon on 28/04/2018 - 08:16
        +3

        My understanding is that the wheels turn the motor to regenerate energy through braking. I don’t think you can extract energy from hot discs to power a car so the brakes will not wear out faster.

        • ozb10 on 28/04/2018 - 08:35

          If that's how it works, that sounds good.
          Will definitely consider one when there are more charging stations around or that I can fully recharge the car in 3-4 minutes at fuel stations.

        • D C on 28/04/2018 - 10:51

          @ozb10:

          If that's how it works, that sounds good.

          Yeah, that's how it works. Motor spins backwards and becomes a generator, charging the battery. That's how electric cars do engine braking.

          Going downhill they're probably smart enough to control how much the battery charges so providing just enough load to slow you to the road limit. Or maybe not, who knows.

        • Chris Topher on 30/04/2018 - 10:33

          @D C: I'm fairly sure the energy goes backwards(? O^O {reverses direction (makes, not uses)}) not the motor. :-/

        • D C on 30/04/2018 - 15:38

          @Thatwey:

          I'm fairly sure the energy goes backwards

          Right, and how does that happen?

          It comes down to using DC motors which can be used as generators. Apply power, they spin. Spin them & power comes out. As DC motors are polarised, to get power out you need to turn them in the opposite way to how you were powering them.

          When driving the battery the powers the motor, which then turns the wheels. When the vehicle is slowing down the reverse happens, a gear dis/engages (usually a planetary gear) to reverse the motor direction.

          The battery being charged puts a load on the motor, basically the kinetic energy of the vehicle is forcing the motor to spin, while the battery is trying to stop it. It all balances out eventually.

          You also have straight electric engine braking (no regen) often found on production equipment like lathes. When you want to stop (big machines takes ages to slow down so you can put a new part in and time is money) you just put a dead short on the motor. All the kinetic energy in the machine gets converted to heat. The dead short (usually a big resistor) does get rather warm.

          A lack of kinetic energy is why regen braking on e-bikes is a bit pointless, a lot of effort for little gain.

        • Chris Topher on 01/05/2018 - 20:27

          @D C: The motor continues to rotate in the same direction… it doesn't spin backwards… instead of consuming energy, it generates (produces) energy… that's how. :-)

          Please take note of my question mark (?), brackets (parenthesis), goggle eyes ( O^O ).

          Example: I charge a capacitor with EMF and positive (+) goes in the anode, or cathode if we use electron flow principle, but let's stick with conventional current flow… + goes into the anode, cathode is at ground or 0V. At some point I stop charging the capacitor (or condensor), I then attach a load (a resistive component) between + & -, current the flows from the anode (+) to ground, 0V, cathode.

          Similar but different - the motor uses the energy from the EMF where the capacitor stores it. The motor back-generates energy where the capacitor releases it.

        • D C on 03/05/2018 - 01:16

          @Thatwey:

          Please take note of my question mark (?), brackets (parenthesis), goggle eyes ( O^O ).

          I did, there's a reason they don't let programmers have screwdrivers.

          Your capacitor/resistor example isn't relevant unless you want to explain how the resistor can charge the capacitor back up. (And no-one gives a damn which way the electrons go.)

          My reply could have been worded slightly better, I did notice but eh. You are correct that a DC motor will produce current no matter which way it spins, the key here is polarity; in order to charge the battery the voltage needs to be reversed, and in order to do that the motor needs to spin in the opposite direction.

          There is gearing that reverses the motor spin when it is not being powered.

          When a battery discharges current goes from positive to negative, to charge a battery the voltage needs to be reversed to shove the current in the opposite direction and cause a chemical change to occur.

          Find a little motor out of a toy or something and stick it on a DMM. Then use the DMM to check the voltages on a battery charger. Think about what you have discovered.

        • Chris Topher on 03/05/2018 - 19:39

          @D C: I discovered that I have no idea of how you are trying to explain things, I charge a battery positive to positive… the voltage isn't reversed, the current is higher in th… never mind.

        • D C on 06/05/2018 - 22:45

          @Thatwey:

          I charge a battery positive to positive … the voltage isn't reversed

          Yes it is, think about it.

          Voltage is electrical pressure, right? That pressure causes the current to flow, right?

          I charge a battery positive to positive

          Yes, and why is that? Your battery is a power source and so is the charger, yet you've connected them in parallel? Does that make sense to you?

          Let's try the old favorite analog - water.

          You have a sealed tank full of water, the only outlet is a hose at the bottom. As the tank is full water flows quickly (high pressure), and the flow decreases as the water level (pressure) drops, eventually stopping.

          Your battery is the same, pressure is voltage, and water flow is current. No voltage, no current.

          Now say there's a water wheel at the end of the hose. Water flows and the wheel spins. As the pressure drops the wheel spins slower, and eventually stops.

          How do you fill the tank back up? Simple - to get the water back into the tank you need it to move backwards So you need to reverse the current flow, and for that you spin the water wheel backwards, just like in a car you spin the motor backwards.

          The other method is like your charger. What happens when two batteries with unequal voltages are connected in parallel? Well, current will flow from one to the other until the voltage matches.

          To use a water analogy you get a second tank full of water, and connect the hoses of the two together. The water will flow from the full tank to the empty one until they are at the same level (pressure). The second one needs to be at least as tall as the first, and the taller the second tank the higher its pressure, so the current flow will be higher (hello phone fast chargers!).

          Batteries are the same, the voltage pressure of the charger will be higher than the battery, so a 1.5v battery charger may output 5v. The voltage pressure of the charger is higher than the battery, so the current will flow backwards THROUGH THE BATTERY, causing a chemical reaction - that's what charging IS.

          (The fact that the voltage of the charger is so high is why smart chargers exist, trying to charge a 1.2v battery up to 5v isn't a good idea.)

          As to the car, if the voltage is going in one direction when driving, then for regen the voltage needs to be reversed. The common way is to reverse the motor, often making it run even faster in order to generate a higher voltage than the battery. You can reverse the voltage electrically, but that gets tricky.

          You don't have to believe what I wrote, try it yourself with a toy motor & DMM.

        • Chris Topher on 07/05/2018 - 12:49

          @D C: Mode - that's the word you are missing, motor goes into reverse mode.

        • D C on 07/05/2018 - 17:23

          @Thatwey:

          motor goes into reverse mode

          Reverse mode? No.

          We're not dealing with ESC's and all that. We are not DRIVING the motor, the motor is being DRIVEN. Anyway, so basically:

          Motor spins backwards and becomes a generator

          …which is where we started.

          I think you need to read/watch less and play more.

          Here's something for you to contemplate. For electrons to flow we need a circuit, right? So if I short out a battery they all go from one end to the other.

          Say I connect a capacitor across a battery and it charges up. Now a capacitor is just two plates with an insulator (dielectric) between them. How does the current / electrons move through this circuit if there's an insulator right in the middle?

          (There is an explanation but it's easier to pretend the flow happens anyway.)

  • Findo on 27/04/2018 - 23:43
    +3

    On the comenarra parkway and yanko Rd on Sydney’s upper north shore, people get up to pretty good speeds. Sadly, the cops don’t like cars fighting gravity so they camp there often to catch people going 64km/h in a 60 zone. The best I’ve ever done on Yanko Rd was fly down the first hill at 160, by the time I made it up the second hill I was still going 90+ without having to accelerate up the hill.

    • Chridim on 28/04/2018 - 03:54

      As i started reading the post i thought straight away about Yanko road. I used to turn there to avoid the pacific hwy like many do.
      Even the safest driver can speed to 90 km/h which is just enough to clear the uphill bit without using all your power.

    • ozb10 on 28/04/2018 - 08:15

      Haven't driven that road, I probably won't go as far to 160, but I would most likely speed a bit too if I get to know that road and where the cops might hide.

    • shaybisc on 28/04/2018 - 10:09

      Are there any driveways entering this road?

      • Findo on 28/04/2018 - 12:07

        Plenty, but cars leaving driveways have to give way to cars on the main road. Just do a quick (slow) run beforehand to sus out cops before doing a speed run. Usually if there are cops on the pacific highway there will be cops on the parkway.

        • Quantumcat on 28/04/2018 - 13:46
          +2

          Speeding will make it hard for cars coming into the road to know when it is safe. You may find yourself in an accident if you're going 80 but they think you're going 60 and they have time to come onto the road.

        • shaybisc on 28/04/2018 - 17:58
          +3

          @Quantumcat:

          And if you are leaving your driveway expecting the traffic to be going 60ish and some random idiot is doing 160 …

  • derpdeder on 28/04/2018 - 05:24
    +1

    You may have seen the interesting disucssuion around manual transmission here: https://www.ozbargain.com.au/node/374703

    Speed control is a key benefit of driving a manual - in this situation I would leave it in 3rd on the downhill and you wouldn't go over 60km/h. No braking at all.

    • ozb10 on 28/04/2018 - 08:26

      It still does not solve the problem that I have to use more fuel to go back uphill.

      And although I do have a manual license, I just hate having to change gears while stuck in traffic, so no thanks.

      • derpdeder on 28/04/2018 - 09:15

        Well it solves the problem of breaking the law so there is that.

        • pegaxs on 28/04/2018 - 10:02
          +4

          $0.05 worth of fuel extra, or a $200+ speeding fine… I’m ok with the “extra” fuel than I am with lining the bar tab at the annual policemen’s ball…

    • spackbace on 28/04/2018 - 20:58

      Speed control is a key benefit of driving a manual

      Semi-auto boxes have been around for years, meaning you could do the same thing with an auto…

    • CMH on 30/04/2018 - 18:30

      I drive down a road regularly that even at 3rd gear (revving at >3500rpm) I go from 40kmph at the top to >75kmph at the bottom. It is a 60kmph road.

      If I coasted down from 40 I'd hit about 90.

      There's also another road near my parents' place that I could hit 80kmph on a pushbike. Thank god there's never any speed traps down that one.

      Weird that I could descend down Mt Hotham almost all the way without using brakes (there's a small bit that requires active brakes), but I can't on suburban Melbourne.

  • Windows7forever on 28/04/2018 - 06:37

    This reminds me of driving down River Rd in Lane Cove. The hills are so dramatic you have to break or risk a fine. Cops always fishing.

  • [Deactivated] on 28/04/2018 - 07:08

    Drive a manual car and drive it properly. Overspeeding downhill becomes a thing of the past.

  • rover on 28/04/2018 - 08:46

    Just just traction braking: no wear and tear on the brake pads/discs, free energy, obey the law and keep your fellow man safe.

    It's a win-win-win-win.

  • doctordv8 on 28/04/2018 - 08:50
    +1

    Good topic question. So interesting to read how many members here admit to having disregard for road safety and the law.

    4….I will break and reach around 60-65

    4.5 I will hold at 60. The maximum is 60Kph so therefore I follow as directed, as we all should - & for the unexpected.

    5….I will break to 60 or below

    Just a little outside the rules, then eventually is becomes more and more, and then blatant disregard for many rules.
    So many lives are lost on the roads because speed limits and other rules are taken for granted, so show the car behind your brake lights and hold steady in control at the limit or below - safe speed for conditions. Yeah, I remember being young, inexperienced and stupid - the rules were not to be taken seriously, but I sorta grew up on the roads, thankfully I have not had any serious accidents or otherwise my fault or not, but the near hits from idiots…so many.

    • Eeples on 28/04/2018 - 10:01
      +2

      There is this stop sign near me that almost everyone rolls through….

      When I stop at it I almost get rear ended. Consistently.

      A couple of times I’ve rolled thru because I’m being tailgated and there is no way they won’t hit me if I stop.

      Ridiculous.

  • pegaxs on 28/04/2018 - 09:57

    I would stay at the speed limit becuse that’s what the speed limit is set at. And by the sounds of it, it sounds like it is set up intentionally that slow for the sake of catching drivers out for revenue raising exercises. But being a stupid speed in relation to the area doesn’t give anyone the right to say, “well I can drive faster here because it’s still safe.”

    • D C on 28/04/2018 - 11:27

      it sounds like it is set up intentionally that slow for the sake of catching drivers out for revenue raising exercises.

      Nah, if they set a high limit for just that bit then that's revenue raising. End result is the same, cops ping you at the bottom of the hill where the limit drops back to 60.

      Generally speaking the traffic blokes don't like randomly changing the speed limits, it buggers up traffic flow (speed up, slow down, speed up, etc), a single limit is better. And that limit is determined by the worst bit of road in the worst conditions, eg downhill curves in the rain.

    • Diji1 on 28/04/2018 - 12:18

      it sounds like it is set up intentionally

      Yeah, setting up 1 speed limit across two hills sounds like a major setup.

      • D C on 28/04/2018 - 17:34

        1 speed limit across two hills

        Right.

        So instead let's have one speed limit for down the hill and one for up the hill, and determine the limit based on the grade; steeper downhill = higher limit.

        So now you've a different speed limit every few hundred metres, and still getting pinged because you didn't brake at the bottom of the hill where the limit changes.

        Sounds great.

    • doctordv8 on 29/04/2018 - 23:40
      -1

      The idea of revenue raising was bantered about by drivers that do not take limits and roads rules seriously, and or do not/can see the potential for accidents or past their greedy wallets.
      If you break the road rule and get caught, you are at fault. That is not revenue raising no matter the location.
      Besides, the traffic police do not design roads and or the rules on that road, so again, no revenue raising.

      • pegaxs on 30/04/2018 - 01:11
        +1

        I cannot speak for other states, but in NSW, your payment for any fine of this nature, ie: issued by the police, goes to the NSW state revenue office…

        If it is not “revenue”, then what is it?

        There are times when police will enforce legislation upon people in the hope that they will just cough up. One only has to look at the court system and the sheer amount of people fighting traffic infringements. Some of the road rules are so obscure that I doubt that you would even know all of them, let alone be 100% compliant at all times while driving.

        While I am glad that road rules do exist, at times the police extend the letter of the law a little to liberally under instructions from their commanding officers. The state budget and police force in particular is budgeted against the collection of these traffic infringements. The issuing of these infringements directly pays for things like police and other infrastructure. If it was not for traffic fines, there would be a massive hole in the states budget that would need to be filled by some other means.

        So, if you think that the fines from traffic infringements are punishment and not at all related to revenue, then I suggest you are either a police officer yourself or a politician.

        For the record, the last time I was booked for anything was in 1994. I only know that because on my last RBT stop, the policeman made a comment about it. So, I do take limits very seriously, as with all aspects of driving and I still feel that a majority of the fines handed out to people are bullshit and done purely in the name of revenue and to line the states pockets…

        • doctordv8 on 30/04/2018 - 18:37

          I agree with you in part, punishment first and foremost, budget limits or not. Every cent into the coffers to run the governments regardless of where they come from or how much is the radar gun at the bottom of yhe hill, it is still a punishment. Every cent is also revenue, exactly he same as stamp duty etc.
          Not a policeman or politician, but I am sick of most drivers (many many in here) complaining of paying "revenue" into the coffers after breaking the law. Follow the rules every minute out on the roads, be updated in the rules and changes, and accept it is a privilege even if also a necessity in most situations. But at the end of the day, do the crime - pay the fine, and yes it will be called revenue for that is what it is and what incoming funds are called.

          Lives are more important, but no one here gets upset about that until they are hurt. That is just wrong.

  • myusername on 28/04/2018 - 10:35

    same same but different

  • airzone on 28/04/2018 - 11:44

    Hold the car in a lower gear.

  • Cheeper on 28/04/2018 - 12:01

    Dead simple… if the speed limit is 60 then do 60 or cop a fine.
    The fact that it is up hill or down hill or with a strong tail wind is of no relevance.
    Your car has a break (ha ha) pedal…

    • Diji1 on 28/04/2018 - 12:19

      Better hope it's not break or no brake!

  • The Vat on 28/04/2018 - 21:48

    If I'm the first or only car, there is no way I'm going faster than 60 km/h. Especially in Queensland, where the cops love pulling that bottom of the hill stuff.

  • shrugies on 08/05/2018 - 14:31

    Brake to 50-55, roll to 60-65, repeat.

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