Sydney suburbs sit 34% further from the CBD by road than the straight line says

Where the straight line misleads most

The pattern at the top of this table is entirely geographic. Brisbane Water separates the Bouddi peninsula from the rest of the Central Coast, and the drive tracks around it. The Royal National Park does the same thing to Bundeena and Maianbar. In each case the straight line crosses water that no road crosses.

Source: OSRM driving routes to the Sydney GPO pinned August 2026, against SuburbCost straight-line distances.

Where the straight line is close to right

The other end of the table is a single corridor. Penrith sits at the end of the M4, which runs almost directly at the city, so the road barely deviates from the line. Six of the eight closest suburbs in Greater Sydney are Penrith addresses.

Distance from the city is not one measure

Regentville is 51.7km from the CBD and Wagstaffe is 40.3km. On the straight line Wagstaffe looks like the closer address by 11km. Drive both and Regentville arrives 41km sooner. Two suburbs can carry similar distance figures on a listing and involve completely different journeys, and nothing in the listing tells you which is which.

What the gap costs in commute terms

SuburbCost models the driving commute at the ATO rate of 91c per kilometre over 192 commuting days, tapered by distance. That model runs on straight-line distance, so it understates the drive for almost every suburb. The table below re-runs the same model on the measured road distance, holding every other assumption constant.

Kurnell is the clearest case. It faces the city across Botany Bay, and the drive runs the long way round the bay through Taren Point. Tempe and Wolli Creek are close to the city in both measures, but the Cooks River and the airport force the road into a detour that adds two thirds to the trip.

Get the full running-cost breakdown for any Sydney suburb →

What this means for our own figures

Our commute numbers are modelled on straight-line distance, so for most Sydney suburbs they are too low. The median suburb would carry about $524 a year more if the same model ran on road distance. We are publishing that rather than quietly adjusting it, for two reasons.

The first is that the ranking barely moves. Almost every suburb is understated, so the order of a cheapest-to-dearest table stays close to the same even though the levels shift. The second is that the correction is not uniform, and applying an average multiplier would introduce a different error. A flat 1.34 would overstate Penrith by a quarter and still understate Bundeena by a third.

The honest position is that a straight-line commute figure is a floor. Read it as the minimum, then look at the road ratio for the suburb you care about.

Where the model reaches its ceiling

Three suburbs in this set cross a threshold rather than shift within it. Mangrove Creek is 57.7km in a straight line and 109.8km by road, Lower Mangrove 51.7km and 101.3km, and Spencer 46.8km and 107.8km. All three sit inside the 100km taper on the straight line and beyond it by road, so on road distance they would move to the flat regional driving allowance of $18,200 rather than a tapered figure. They are excluded from the table above because the change is a change of category, not of degree.

Penrith is the far-west reference point here, see its current rates and cost any suburb in the area →