The Halcema Highway is traveled by the most civilized drivers in da Peelipins. Here, a certain etiquette prevails.
Right of way is always given to vehicles going uphill. When it's technically too difficult for a downward driver to pull over or back up, the upward driver will concede. No hard feelings, no shouts of 'ukinnam!' or 'butum!' or 'takkim!'. (Although, some drivers are known to mutter this under their breath.)
A slower driver will ALWAYS signal or pull over when it's safe for a faster driver to overtake.
'Thank yous' and 'your welcomes' are always exchanged between drivers who have given way, and drivers who get their way. A nod of the head, a wave of the hand, or a quick beepbeep on the busina.
When road repairs are underway, or landslides are being cleared, drivers and passengers patiently wait in line. NOBODY tries to drive up to the front and make singit. If you're fast, you'll be allowed to overtake later anyway.
Vehicles slow down when driving through towns. Why? Somewhere in Buguias a sign says on a short, steep, accident-prone climb through town, "SLOW UP." Somewhere in Bauko a sign says, "Drive slow, see our town. Drive fast, see our jail." Somewhere in Sabangan a sign says, "SLOW DOWN. CHILDREN PLAYING ON ROAD." (Also in Sabangan where a portion of the road is under repair, a sign says, "Caution. Good-looking Igorots at Work." Definitely worth slowing down for!)
There are a few irritating, uncouth, uncivilized exceptions: Rising/Racing/Rushing Sun buses, the brash new generation of young drivers of commuter vans who never drove on the Halcema back when the cost of a small mistake was extremely high, and ignorant tanga-manilas on their way to Sagada who crawl at an overly cautious 20kph and think they're still in their stinking city where the driving rule of thumb is "Own the road. Let no one get ahead of you."