Category: Highway Engineering

Every institution that governs Indian roads today — the funding mechanism, the technical body that writes the standards, the national research laboratory — can be traced back to one committee appointed in 1927. This post explains why that committee was needed, what it recommended, and how each of its four recommendations turned into an institution…

The story of road building is really the story of one idea slowly being discovered — that a road’s strength does not come from how much stone you pile into it, but from how well it is drained and how well the stones lock together. It took nearly two thousand years to arrive at that…

Volume tells you how many vehicles are using a road. Capacity tells you how many could. And level of service tells you something neither of those numbers captures — what the journey actually feels like. This post covers the three types of capacity, the capacity formulas, the six levels of service, passenger car units, and the IRC capacity…

A spot speed study tells you how fast vehicles pass one point. What it cannot tell you is where they slow down and why. For that you have to travel the road with the traffic — and that is what a speed and delay study does. This post covers speed and delay studies, the floating car…

Speed sounds like a simple thing to measure until you try. Ask “how fast is traffic moving on this road?” and you immediately face a choice — do you mean at a particular point or over a length? Do you average the speeds of vehicles, or the time they take? Those choices give different numbers, and…

Raw traffic counts are almost useless. A notebook containing thousands of tally marks tells you nothing until it is organised into a form that answers a question. This post covers the standard ways traffic volume data is presented — and in particular the 30th highest hourly volume, which is one of the most reliably asked topics…

Traffic volume is the simplest thing you can measure about a road, and also the most useful. Almost every other decision in traffic engineering — how many lanes, how thick the pavement, whether a signal is justified — begins with a count. This post covers what traffic volume is, the formula for calculating it, why…

You cannot fix a problem you have not measured. Before any road is widened, any signal installed, or any bypass planned, somebody has to go out and count what is actually happening — how many vehicles, how fast, going where, stopping when. That measuring work is called traffic studies, and this post covers all seven types,…

Of everything a vehicle does, stopping is the one function on which safety most directly depends. A vehicle that cannot accelerate well is merely slow. A vehicle that cannot stop well is dangerous. This post covers braking characteristics, the third of the three areas studied under traffic characteristics, and shows how braking behaviour feeds into three…

Roads are not designed around an average vehicle. They are designed around the demanding ones — the widest, the heaviest, the longest, the slowest to climb. Every dimension of a highway can be traced back to some property of a vehicle that had to be accommodated. This post works through the four vehicular characteristics that matter, and…