What Is Success for Projects and Programs?
What constitutes success seems to depend on where you’re standing.
If you are standing on the project side of the fence, the orthodox measures of success revolve around controlling inputs: time, money and the specification.
“On-time, on-budget and to spec” – the so-called “iron triangle”.
However, if you are standing on the business side of the fence, you don’t commission projects to perform against time, money and specifications - you commission projects to achieve the value that comes out of the project.
While for decades, we have measured project success in terms of how the project performs against the inputs used, the true measure of success is how well the project or program delivers output. 
As a business executive, I want my desired and (hopefully) specified outcomes and benefits delivered for an acceptable level of inputs. The inputs – time, cost and quality – determine the net value of my desired outcomes and benefits. But having a project deliver ‘on time/on budget’ is not my primary objective. Jed Simms
The simple reason why we have used time and cost to measure success is becuase many of our project mental models have come from construction where these proxy measures are a reasonable indicator of progress.
A project delivered ‘on time/on budget/to specification’, that fails to deliver the intended desired business outcomes, benefits and value in full is still a failure. Note “failure” is a lack of success.
A consulting project manager with over thirty years of delivery experience recently recounted how she had eventually realized after 20+ years that ‘on-time…’ measures were not what the customer wanted and excellence in this area would not placate them if they saw they had not received the expected value from their investments.
In the literature on ‘project success’, it is only since around 2005 that academia consistently acknowledged that the orthodox input measures are inadequate. Worryingly, some of these articles suggest some additional measures are needed, such as for project team satisfaction and enjoyment
Measuring Success by the Wrong Measures Leads to Wrong Decisions
An overly zealous focus on time and cost management can lead project decisions to be made that destroy the business value in order to ‘save project costs’. Keeping within the project budget is good and to be applauded – but not at the expense of destroyong the purpose of the project.
We recently saw one project that eliminated $6m in benefits to save $400,000 in costs. Not a wise trade-off.
The importance of choosing the inputs v outputs as measures of success.
The importance of choice between input and output definitions of project/program success is in the business results and value delivered.
An output-based business outcome, benefits and value measure of success creates and sustains a focus on the delivery of all the available business value.
However, an input-based project time, cost and specification measure of success creates and sustains a focus on the project and its internal constraints, with the business results taking second or third place in the priority spectrum.
The input measures approach allows scope changes, designs and project execution decisions to be made that destroy business value – decisions that could have been avoided (or at least substantially mitigated) with an outputs-based success measurement process.
Your choice of success measure will determine if your project will be value or cost focused – whether it will maximize the business value delivered or just manage the project costs of delivery.
TOP’s measure of project/program success is:
“The delivery of the agreed desired business outcomes, their associated business benefits and optimized net value.”