How Cambr Scores a Driving Road

The question

Why score roads at all

Every navigation app in the world optimises for arrival time, and they are right to. Almost every journey anyone makes is about getting somewhere.

The problem is that nothing measures the other thing. Ask which road between two points is the better drive and the honest answers available to you are a magazine list of ten famous roads, a forum thread from 2014, or local knowledge you only have where you live. None of that scales, and none of it helps when you are two hundred miles from home with an afternoon spare.

So we built something that does scale. The question Cambr answers is narrow and specific: how good is this road to drive?

Cambr road detail for A821 Duke's Pass scored 86.5, showing the six scoring factors and its S tier badge

The algorithm

The six things the algorithm measures

Tap any road in Cambr and you see the same six factors, with the road’s result against each.

01

Corners

How much the road turns, how often, and whether the turning is sustained or arrives in one short burst. A road that corners continuously for twelve miles is a different proposition from one with four good bends and a lot of straight.

02

Climb

Elevation gained and lost, and how dramatically. Gradient changes what a corner asks of you and what the road feels like from the driver’s seat.

03

Scenery

How much of the road runs through a national park, an area of outstanding natural beauty or equivalent protected landscape. It turns out to be a strong predictor. Almost every road anyone rates highly runs through land somebody else already decided was worth protecting.

04

Flow

Whether you can actually get a rhythm going. This is the one most lists ignore. A technically superb road that is full of traffic, interrupted by villages or capped at 40 is not delivering what it looks like it should on a map.

05

Width and surface

How wide the road physically is, and what condition it is in. Width matters more than people expect. A road you cannot commit to because you are watching for oncoming traffic is a worse drive than a slower road you can read.

06

Road type

What class of road it is. B-roads and secondary A-roads score best, which matches what the press has been saying for thirty years. Trunk roads and dual carriageways score badly or are excluded entirely.

The editorial layer

The press layer

The algorithm is only half of it.

Evo, Top Gear, Autocar, PistonHeads, Rush and a couple of dozen other publications have been arguing about Britain’s best roads for decades. That argument is evidence. A road that a dozen journalists have driven, written up and returned to is telling you something that no amount of geometry can.

So every founding road carries a second input built from that coverage, and the two are combined into the score you see. For most roads the two agree, and the editorial layer just confirms what the measurement found.

The interesting cases are the ones where they don’t.

Evo
Top Gear
Autocar
PistonHeads
Rush
and a couple of dozen others

Worked examples

Three roads that show how it works

S

A821 Duke’s Pass

86.5

The straightforward case. The algorithm rates it 88.63 and the press layer agrees. Its corner score is a perfect 25 out of 25, its flow is 11.8 out of 13, and the road’s press reputation adds 9.9 on top. Everything points the same way, and it lands comfortably in S tier.

A

A543 Evo Triangle

76.6

The opposite case. On measurement alone the A543 across the Denbigh Moors scores 63.04, a B-tier road: fast and open, it turns and climbs less than the roads the algorithm rates highest. The press layer lifts it to 76.6 and A tier. This is one leg of the Evo Triangle, named after the magazine that has tested cars on it for years, and the people who know it best rate it far higher than its geometry does.

B

Hardknott Pass

66.9

The algorithm loves Hardknott. It scores 83.48, which would put it among the best roads in the country. Then the editorial layer pulls it down to 66.9 and B tier, because for all its reputation as the hardest road in England, the driving press has never really endorsed it as a good drive. A 1-in-3 gradient on a single-track lane with blind hairpins is a test, and a test is not the same as a great road. The score reflects that, and plenty of people will disagree with it.

Those three are the argument for having two layers at all. An algorithm on its own would put Hardknott near the top. Press coverage on its own would miss every unnamed B-road in the Pennines that nobody has written about.

The tiers

Tier	Score	What it means
S	77 and above	22 roads currently. The ones worth planning a trip around
A	67 to 76.9	Excellent roads worth a detour
B	55 to 66.9	Good backroads worth taking when you are nearby
Not shown	Below 55	Not surfaced in the app

Roads the algorithm discovers on its own cannot reach S tier. S requires editorial backing, because a road nobody has ever written about might still be excellent and we would rather be slow to canonise it than wrong.

Cambr route options to Cheddar Gorge: Fastest, Quick, Driver's Route and Extended, each bar coloured by the tiers of road it uses

Cambr Active Drive on a loop from Brecon, with the A4069 Black Mountain Pass scored 85.0 and the roads ahead in tier colours

On the road

What makes every drive different

The score describes the road. These four things shape the drive you actually get on it.

Surface on the day

Road condition changes with the season, the weather and whoever last patched it. Drivers spot it first, which is exactly what reviews in the app are for: rate a road and say why, and the score everyone else sees moves with it.

How good the corners are

Cambr measures how much a road turns. How good the turning is, the clear sight line and honest camber that make one ninety-degree bend a joy and the same bend blind and off-camber a chore, is where driver reviews earn their keep.

Your car

A narrow, bumpy, committed road is a brilliant drive in a light car and a nervous one in something wide and fast. The score describes the road, and you know your car: put the two together and you’ll know which roads to point it at.

The day

Traffic, weather, light and time of year move the experience more than a couple of points of score ever will. Glen Coe in October at seven in the morning and Glen Coe in July at midday are not the same road.

Versions

How scores change

Scores are not fixed. They move when the algorithm improves, when new press coverage lands, and when drivers rate roads in the app.

Every Cambr user can rate a road out of ten with reasons, and those ratings feed back into what everyone else sees. Surface in particular is something the people driving a road know long before any dataset does. That feedback loop is the part of this that gets better with every drive.

The scoring version is published on this page and changes when the algorithm does. The current version is v3.6.

Rating a road in Cambr: a score out of ten, what stood out and what let it down

The recipe

What we don’t publish

The exact weights, the formula and the full scored dataset stay private. That is the work, and it is the thing a competitor would copy first.

Everything else is here: what we measure, why we measure it, where the editorial layer comes from, and what makes every drive different.

Questions

How many roads has Cambr scored?

Every driving road in Britain and Ireland, swept region by region. 152 of them are editorially validated founding roads with a press layer; the rest are scored algorithmically.

Can a road’s score go down?

Yes. Scores are recalculated when the algorithm changes, and roads move between tiers when they do. We would rather correct a score than defend an old one.

Why is a road I love rated badly?

Most often it’s flow, width or road type. A road that’s wonderful to ride a bike along or beautiful to look at can still score poorly as a drive. If you think we have it wrong, rate it in the app and say why. That’s the mechanism.

Do you score roads outside the UK?

Yes. Ireland is scored and on the map, and 71 European roads are on there too. Turn-by-turn routing covers Great Britain today, with Ireland and Europe on the way.

Is the score about speed?

No. Nothing in the score rewards driving fast, and camera coverage counts against a road because constant enforcement changes how it feels, not because we think you should be speeding on it.

The 10 best driving routes in the UK, ranked by how much of each drive is on a top-tier road.

How Cambr scores a driving road.