What TfL’s Sustainable Access Measure means for development in London

For more than two decades, one question has shaped the density, height and parking of almost every development in London: what’s the PTAL?

The draft London Plan changes that.

Published on 16 July 2026, it introduces TfL’s Sustainable Access Measure (SAM), a measure of travel times to jobs, services and amenities by public transport and walking, developed by TfL to inform land use policy and integrate it with transport planning.

Members of the mode transport team recently attended a TfL session on SAM. Alongside our own review of the draft Plan and its evidence base, Adam Ford shares our take on what the new metric is, how it will be used, and what developers and landowners should be thinking about now.

What SAM measures

PTAL measures how well a site is connected to the public transport network, considering factors such as walking distance to stops and stations, service frequency, reliability and waiting times.

However, it does not consider where those services can take residents or the opportunities and services they can reach.

SAM shifts the focus from proximity to reach, considering not just how close a site is to public transport, but what residents can access through the network.

SAM is calculated for every 100m grid square in Greater London, the same resolution as PTAL, giving a score for over 150,000 locations.

The score combines three layers:

• City-wide public transport (60 minutes): access to jobs across London.

• Other public transport (30 minutes): access to regular non-work destinations such as schools, healthcare, food shopping and green space.

• Walking (10 minutes): access to those same everyday destinations on foot.

Destinations are weighted by how often Londoners travel to each type of place by each mode, using the London Travel Demand Survey.

The three layers are then combined using weights derived from regression against 2021 Census car ownership. SAM is calibrated to predict where households are less likely to own a car.

Further explanation from the TfL session on SAM

At the TfL session, three further points were made:

• Cycling is excluded for now. The quality of cycle infrastructure varies too much across London to model reliably.

• The assessment reflects AM peak conditions.

• The GLA boundary is not a hard cut-off for destinations. Amenities beyond it count towards scores within London.

As SAM’s scores change more gradually rather than falling away sharply with walking distances as PTAL does, it can distinguish far better between Outer London locations. Places that previously all sat around PTAL 2 can now be meaningfully separated.

Why SAM matters: density, height and parking

SAM is not just a descriptive tool. It is embedded in the policies that decide what can be built.

Density

Under draft Policy MBUL2, the new Optimisation Framework applies to sites over 0.25 ha in SAM 2 and above. It sets height and density ranges by SAM band and character setting.

For a predominantly outer suburban site (Setting A), the range runs from 3-4 storeys at 220-410 habitable rooms per hectare in SAM 2, up to 4-7 storeys at 500-830 hr/ha in SAM 5B.

Residential schemes are expected to achieve the stated minimum densities unless site-specific constraints limit them, and failure to meet the policy carries very significant weight in decisions.

Height

Locations for tall buildings of 30m and above should generally have very good sustainable transport connectivity, which the draft Plan equates to SAM 4 or above.

Parking

The draft Plan introduces a new approach to car parking standards based on SAM and the Optimisation Framework, reinforcing car-free and car-lite development through Policy GHR11.

At the TfL session, SAM 5A and 5B locations were identified as potentially supportive of car-free development.

A site’s SAM level and character setting can be checked on the GLA’s online Planning Data Map. We would recommend doing so at the site appraisal stage for any London opportunity.

SAM and PTAL: complementary, not a replacement

Some commentary has described TfL’s Sustainable Access Measure as replacing PTAL. TfL’s position is clear that it does not, and that the two should be used together.

TfL describes SAM as a London-wide comparator that sets a site’s overall density and permitted parking. PTAL remains a local comparator, used to decide which part of a site takes the taller elements and to test local changes such as a new bus service or walking route.

TfL also indicated that SAM should generally be preferred to DfT’s Connectivity Tool in London. Londoners tend to walk further and commute for longer than the national average, so a metric tuned to national behaviour is less representative here.

The DfT tool may still be useful for access to specific land uses such as healthcare or schools.

For Transport Assessments, we expect both SAM and PTAL to be reported going forward, with SAM carrying the policy weight on density and parking.

Five considerations before relying on the Sustainable Access Measure

A SAM band is a rank, not an absolute score

TfL banded SAM by quintiles of London’s area, subdividing the top and bottom quintiles into 1A/1B and 5A/5B.

It is a 2026 snapshot

There is currently no timeline for future-year forecasting or for updates reflecting service changes. TfL suggested future versions could incorporate committed schemes such as the proposed DLR extension to Thamesmead or the West London Orbital Overground Line, but for now the scores do not reflect planned investment.

SAM cannot yet be adjusted or replicated by applicants

Several of SAM’s inputs, including OS Points of Interest, the OS walk network and TfL’s internal journey times, are not openly licensed.

This is a key difference from PTAL. It has long been common practice to undertake manual PTAL calculations where the published figure misrepresents a site, for example to reflect a new pedestrian access point or planned and proposed changes to bus services.

With SAM there is currently no equivalent route, so applicants may have less scope to make their own case for a site’s sustainable transport credentials.

SAM carries limited weight today

Until the London Plan is adopted, limited weight will be given to SAM, increasing as the Plan progresses through examination. That does not stop it being used now, particularly as current policy already requires connectivity to be assessed and this is a tool developed by TfL.

SAM does not cover the Green Belt

This is the point we consider most significant. The draft Plan’s SAM map shows Green Belt and Metropolitan Open Land as a separate category, and SAM does not appear to be calculated for that land.

The Green Belt gap

The draft Plan’s case for SAM is that distance to a stop is an inadequate measure of sustainable access.

Yet for the only part of London where genuine new settlements are proposed, it reverts to a distance threshold of 1,200m from a qualifying station or proximity to a bus corridor. These tests are binary in that land at 1,150m from a station qualifies, while land at 1,250m does not.

A site 1,600m from a station with six trains per hour may well offer more journey opportunities than one at 1,000m from a station with two. That is precisely TfL’s own argument for moving beyond PTAL, and it applies equally to Green Belt locations.

Extending SAM, or an equivalent destination-based measure, to Green Belt land would make the Plan’s approach to accessibility consistent across London. The same applies to bus corridors, where the quality, frequency and destinations of the routes matter far more than simply being within walking distance of one.

What to consider now

The draft London Plan consultation closes on 15 October 2026, and TfL has explicitly invited feedback on SAM itself. For anyone promoting sites or preparing applications in London, we recommend the following:

• Check the SAM band and character setting of your sites now and understand where they sit against the Optimisation Framework.

• Identify sites close to a band boundary, where the score has the greatest consequences and is least straightforward to verify.

• Report SAM alongside PTAL in Transport Assessments and Statements, recognising its currently limited but growing weight.

• For Green Belt or edge-of-settlement land, consider how accessibility can be evidenced beyond the policy’s distance thresholds.

• Consider whether to respond to the consultation before the deadline.

mode is advising clients on the implications of the draft London Plan, including SAM, the Optimisation Framework and Green Belt accessibility.

To discuss what SAM means for your site, please get in touch.