Transverse momentum fluctuations in nuclear collisions at<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mn>158</mml:mn><mml:mi>A</mml:mi><mml:mspace width="0.3em"/><mml:mi mathvariant="normal">GeV</mml:mi></mml:mrow></mml:math>

Results are presented on event-by-event fluctuations in transverse momentum of charged particles, produced at forward rapidities in $\mathrm{p}+\mathrm{p}$, $\mathrm{C}+\mathrm{C}$, $\mathrm{Si}+\mathrm{Si}$, and $\mathrm{Pb}+\mathrm{Pb}$ collisions at $158\phantom{\rule{0.3em}{0ex}}A\mathrm{GeV}$. Three different characteristics are discussed: the average transverse momentum of the event, the ${\ensuremath{\Phi}}_{{p}_{T}}$ fluctuation measure, and two-particle transverse momentum correlations. In the kinematic region explored, the dynamical fluctuations are found to be small. However, a significant system size dependence of ${\ensuremath{\Phi}}_{{p}_{T}}$ is observed, with the largest value measured in peripheral $\mathrm{Pb}+\mathrm{Pb}$ interactions. The data are compared with predictions of several models.