Contract clauses may be modified from time-to-time by mutual agreement between the parties. Original designs and intentions are unlikely to survive intact the changes in demands and technologies occurring over spans of twenty years or more. Variations (including re-allocating risks) may be justifiable in terms of technical obsolescence (e.g. tolling systems); new legal/political requirements (e.g. health and safety; changes in service user demand) (Partnerships Victoria 2001, p.135; Edwards et al 2004, p.122); from decisions to modify the length of agreements as a result of scope change; and for private partner under-performance (Partnerships Victoria 2001, p.161).
In the case of under-performance, the public partner will normally reserve the right to intervene if the quality of services provided by the private partner fails to meet its obligations (Partnerships Victoria 2001, p.161). This could arise from a breach of contract such as default (through continued acts of non-compliance) (Partnerships Victoria 2001, p.148); through major default (such as insolvency); or in an emergency where the public partner may assume operational control for a period of time because the situation may be beyond the capability of the private partner to deal with it effectively (Partnerships Victoria 2001, p.161). The public partner must be aware of, and plan for, the possibility of intervention.